1
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Nguyen NP, Laird BB. Generation of Amorphous Silica Surfaces with Controlled Roughness. J Phys Chem A 2023; 127:9831-9841. [PMID: 37938899 DOI: 10.1021/acs.jpca.3c04955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Amorphous silica (a-SiO2) surfaces, when grafted with select metals on the active sites of the functionalized surfaces, can act as useful heterogeneous catalysts. From a molecular modeling perspective, one challenge has been generating a-SiO2 slab models with controllable surface roughness to facilitate the study of the effect of surface morphology on the material properties. Previous computational methods either generate relatively flat surfaces or periodically corrugated surfaces that do not mimic the full range of potential surface roughness of the amorphous silica material. In this work, we present a new method, inspired by the capillary fluctuation theory of interfaces, in which rough silica slabs are generated by cleaving a bulk amorphous sample using a cleaving plane with Fourier components randomly generated from a Gaussian distribution. The width of this Gaussian distribution (and thus the degree of surface roughness) can be tuned by varying the surface roughness parameter α. Using the van Beest, Kramer, and van Santen (BKS) force field, we create a large number of silica slabs using cleaving surfaces of varying roughness (α) and using two different system sizes. These surfaces are then characterized to determine their roughness (mean-squared displacement), density profile, and ring size distribution. This analysis shows a higher concentration of surface defects (under-/overcoordinated atoms and strained rings) as the surface roughness increases. To examine the effect of the roughness on surface reactivity, we re-equilibriate a subset of these slabs using the reactive force field ReaxFF and then expose the slabs to water and observe the formation of surface silanols. We observe that the rougher surfaces exhibit higher silanol concentrations as well as bimodal acidity.
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Affiliation(s)
- Nuong P Nguyen
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
- Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Brian B Laird
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
- Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
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2
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Liu M, Liu H, Peng H. Orientational wetting and dynamical correlations toward glass transition on the surface of imidazolium-based ionic liquids. J Chem Phys 2022; 157:034701. [DOI: 10.1063/5.0099845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Surface induces many fascinating physical phenomena, such as dynamic acceleration, surface anchoring, and orientational wetting, and, thus, is of great interest to study. Here, we report classic molecular dynamics simulations on the free-standing surface of imidazolium-based ionic liquids (ILs) [C4mim][PF6] and [C10mim][PF6]. On [C10mim][PF6] surface, a significant orientational wetting is observed, with the wetting strength showing a diverging tendency. Depth of the wetting was captured from the density and orientational order profile by a static length, which remarkably increases below the temperature Tstat upon cooling down. The dynamical correlation length that measures the distance of surface-dynamics acceleration into the bulk was characterized via the spatial-dependent mobility. The translational correlation exhibits a similar drastic increment at Tstat, while the rotational correlation drastically increases at a lower temperature Trot. We connect these results to the dynamics in bulk liquids, by finding Tstat and Trot that correspond to the onset temperatures where the liquids become cooperative for translational and rotational relaxation, respectively. This signifies the importance of collective dynamics in the bulk on the orientational wetting and surface dynamics in the ILs.
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Affiliation(s)
- Min Liu
- School of Materials Science and Engineering, Central South University, 932 South Lushan Rd., 410083 Changsha, China
| | - Huashan Liu
- School of Materials Science and Engineering, Central South University, 932 South Lushan Rd., 410083 Changsha, China
| | - Hailong Peng
- School of Materials Science and Engineering, Central South University, 932 South Lushan Rd., 410083 Changsha, China
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3
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Shen R, Bai Q, Li Y, Guo Y, Zhang P. Influence of ionic strength and surfactant concentration on the alkane contaminant desorption in solution: A molecular dynamics simulation. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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4
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Li Y, Annamareddy A, Morgan D, Yu Z, Wang B, Cao C, Perepezko JH, Ediger MD, Voyles PM, Yu L. Surface Diffusion Is Controlled by Bulk Fragility across All Glass Types. PHYSICAL REVIEW LETTERS 2022; 128:075501. [PMID: 35244425 DOI: 10.1103/physrevlett.128.075501] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 01/07/2022] [Indexed: 06/14/2023]
Abstract
Surface diffusion is vastly faster than bulk diffusion in some glasses, but only moderately enhanced in others. We show that this variation is closely linked to bulk fragility, a common measure of how quickly dynamics is excited when a glass is heated to become a liquid. In fragile molecular glasses, surface diffusion can be a factor of 10^{8} faster than bulk diffusion at the glass transition temperature, while in the strong system SiO_{2}, the enhancement is a factor of 10. Between these two extremes lie systems of intermediate fragility, including metallic glasses and amorphous selenium and silicon. This indicates that stronger liquids have greater resistance to dynamic excitation from bulk to surface and enables prediction of surface diffusion, surface crystallization, and formation of stable glasses by vapor deposition.
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Affiliation(s)
- Yuhui Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Ajay Annamareddy
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Dane Morgan
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Zheng Yu
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Bu Wang
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chengrong Cao
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - John H Perepezko
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M D Ediger
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Lian Yu
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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5
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Han D, Zhou DL, Guo QY, Lin X, Zhang Q, Fu Q. Engineering the Surface Pattern of Microparticles: From Raspberry-like to Golf Ball-like. ACS APPLIED MATERIALS & INTERFACES 2021; 13:31215-31225. [PMID: 34169717 DOI: 10.1021/acsami.1c08663] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.
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Affiliation(s)
- Di Han
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - Dai-Lin Zhou
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - Qing-Yun Guo
- South China Advanced Institute for Soft Matter Science and Technology, School of Molecular Science and Engineering, South China University of Technology, Guangzhou 510640, P. R. China
| | - Xiong Lin
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - Qin Zhang
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - Qiang Fu
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
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6
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Annamareddy A, Li Y, Yu L, Voyles PM, Morgan D. Factors correlating to enhanced surface diffusion in metallic glasses. J Chem Phys 2021; 154:104502. [PMID: 33722035 DOI: 10.1063/5.0039078] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The enhancement of surface diffusion (DS) over the bulk (DV) in metallic glasses (MGs) is well documented and likely to strongly influence the properties of glasses grown by vapor deposition. Here, we use classical molecular dynamics (MD) simulations to identify different factors influencing the enhancement of surface diffusion in MGs. MGs have a simple atomic structure and belong to the category of moderately fragile glasses that undergo pronounced slowdown of bulk dynamics with cooling close to the glass transition temperature (Tg). We observe that DS exhibits a much more moderate slowdown compared to DV when approaching Tg, and DS/DV at Tg varies by two orders of magnitude among the MGs investigated. We demonstrate that both the surface energy and the fraction of missing bonds for surface atoms show good correlation to DS/DV, implying that the loss of nearest neighbors at the surface directly translates into higher mobility, unlike the behavior of network-bonded and hydrogen-bonded organic glasses. Fragility, a measure of the slowdown of bulk dynamics close to Tg, also correlates to DS/DV, with more fragile systems having larger surface enhancement of mobility. The deviations observed in the fragility-DS/DV relationship are shown to be correlated to the extent of segregation or depletion of the mobile element at the surface. Finally, we explore the relationship between the diffusion pre-exponential factor (D0) and the activation energy (Q) and compare it to a ln(D0)-Q correlation previously established for bulk glasses, demonstrating similar correlations from MD as in the experiments and that the surface and bulk have very similar ln(D0)-Q correlations.
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Affiliation(s)
- Ajay Annamareddy
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Yuhui Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Lian Yu
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Dane Morgan
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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7
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Zhang Z, Ispas S, Kob W. Structure and vibrational properties of sodium silicate glass surfaces. J Chem Phys 2020; 153:124503. [PMID: 33003733 DOI: 10.1063/5.0019514] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using molecular dynamics simulations, we investigate how the structural and vibrational properties of the surfaces of sodo-silicate glasses depend on the sodium content as well as the nature of the surface. Two types of glass surfaces are considered: A melt-formed surface (MS) in which a liquid with a free surface has been cooled down into the glass phase and a fracture surface (FS) obtained by tensile loading of a glass sample. We find that the MS is more abundant in Na and non-bridging oxygen atoms than the FS and the bulk glass, whereas the FS has higher concentration of structural defects such as two-membered rings and under-coordinated Si than the MS. We associate these structural differences to the production histories of the glasses and the mobility of the Na ions. It is also found that for Na-poor systems, the fluctuations in composition and local atomic charge density decay with a power-law as a function of distance from the surface, while Na-rich systems show an exponential decay with a typical decay length of ≈2.3 Å. The vibrational density of states shows that the presence of the surfaces leads to a decrease in the characteristic frequencies in the system. The two-membered rings give rise to a pronounce band at ≈880 cm-1, which is in good agreement with experimental observations.
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Affiliation(s)
- Zhen Zhang
- Laboratoire Charles Coulomb, University of Montpellier, CNRS, F-34095 Montpellier, France
| | - Simona Ispas
- Laboratoire Charles Coulomb, University of Montpellier, CNRS, F-34095 Montpellier, France
| | - Walter Kob
- Laboratoire Charles Coulomb, University of Montpellier, CNRS, F-34095 Montpellier, France
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8
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Jagannathan JR, Diemoz KM, Targos K, Fettinger JC, Franz AK. Kinetic and Binding Studies Reveal Cooperativity and Off-Cycle Competition for H-Bonding Catalysis with Silsesquioxane Silanols. Chemistry 2019; 25:14953-14958. [PMID: 31448459 DOI: 10.1002/chem.201903693] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Indexed: 01/23/2023]
Abstract
The catalytic activity, kinetics, and quantification of H-bonding ability of incompletely condensed polyhedral oligomeric silsesquioxane (POSS) silanols are reported. POSS-triols, a homogeneous model for vicinal silica surface sites, exhibit enhanced H-bonding compared with other silanols and alcohols as quantified using a 31 P NMR probe. Evaluation of a Friedel-Crafts addition reaction shows that phenyl-POSS-triol is active as an H-bond donor catalyst whereas other POSS silanols studied are not. An in-depth kinetic study (using RPKA and VTNA) highlights the concentration-dependent H-bonding behavior of POSS-triols, which is attributed to intermolecular association forming an off-cycle dimeric species. Binding constants provide additional support for reduced H-bond ability at higher concentrations, which is attributed to competitive association. POSS-triol self-association disrupts H-bond donor abilities relevant for catalysis by reducing the concentration of active monomeric catalyst.
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Affiliation(s)
- Jake R Jagannathan
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, USA
| | - Kayla M Diemoz
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, USA
| | - Karina Targos
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, USA
| | - James C Fettinger
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, USA
| | - Annaliese K Franz
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, USA
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9
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The Relevance of Point Defects in Studying Silica-Based Materials from Bulk to Nanosystems. ELECTRONICS 2019. [DOI: 10.3390/electronics8121378] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The macroscopic properties of silica can be modified by the presence of local microscopic modifications at the scale of the basic molecular units (point defects). Such defects can be generated during the production of glass, devices, or by the environments where the latter have to operate, impacting on the devices’ performance. For these reasons, the identification of defects, their generation processes, and the knowledge of their electrical and optical features are relevant for microelectronics and optoelectronics. The aim of this manuscript is to report some examples of how defects can be generated, how they can impact device performance, and how a defect species or a physical phenomenon that is a disadvantage in some fields can be used as an advantage in others.
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10
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Fossati PCM, Rushton MJD, Lee WE. Atomic-scale description of interfaces in rutile/sodium silicate glass-crystal composites. Phys Chem Chem Phys 2018; 20:17624-17636. [PMID: 29926862 DOI: 10.1039/c8cp00675j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work interfaces between (Na2O)x(SiO2)1-x glasses (for x = 0.0, 0.1 and 0.2) and TiO2 crystals are simulated using molecular dynamics and empirical potentials. Interfaces are presented for the distinct terminating surfaces of TiO2 with Miller indices ≤2, the properties of which have been investigated using atomistic models. Simulations showed that partially ordered layers had been induced in the glass close to the interfaces, with successive oxygen-rich and cation-rich planes being noted. The first silicate layer in contact with the crystal tended to be highly-structured, with Si ions occupying well-defined positions that depend on the orientation of the crystal at the interface, and showing 2-dimensional ordering depending on glass composition. Finally, interface energies were calculated. These indicated that the interface formation may stabilise a crystal surface in comparison to maintaining a free surface. Results are presented suggesting that the structural flexibility of the glass network allows it to conform to the crystal, thereby providing charge compensation and avoiding large relaxation of the crystal structure close to the interfaces. Such interfacial properties could be crucial to improving phenomenological models of glass-crystal composite properties.
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Affiliation(s)
- Paul C M Fossati
- Department of Materials, Imperial College London, London SW7 2AZ, UK.
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11
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Molecular Dynamics Simulation of Water Confinement in Disordered Aluminosilicate Subnanopores. Sci Rep 2018; 8:3761. [PMID: 29491348 PMCID: PMC5830603 DOI: 10.1038/s41598-018-22015-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 02/15/2018] [Indexed: 11/17/2022] Open
Abstract
The porous structure and mass transport characteristics of disordered silicate porous media were investigated via a geometry based analysis of water confined in the pores. Disordered silicate porous media were constructed to mimic the dissolution behavior of an alkali aluminoborosilicate glass, i.e., soluble Na and B were removed from the bulk glass, and then water molecules and Na were introduced into the pores to provide a complex porous structure filled with water. This modelling approach revealed large surface areas of disordered porous media. In addition, a number of isolated water molecules were observed in the pores, despite accessible porous connectivity. As the fraction of mobile water was approximately 1%, the main water dynamics corresponded to vibrational motion in a confined space. This significantly reduced water mobility was due to strong hydrogen-bonding water-surface interactions resulting from the large surface area. This original approach provides a method for predicting the porous structure and water transport characteristics of disordered silicate porous media.
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12
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Halbert S, Ispas S, Raynaud C, Eisenstein O. Modelling the surface of amorphous dehydroxylated silica: the influence of the potential on the nature and density of defects. NEW J CHEM 2018. [DOI: 10.1039/c7nj03922k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nature and density of defects on the amorphous dehydroxylated silica surface are studied by molecular dynamics for information on the silanol groups of pretreated silica.
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Affiliation(s)
| | - Simona Ispas
- Laboratoire Charles Coulomb (L2C)
- UMR 5221
- Univ. Montpellier
- CNRS
- Montpellier
| | | | - Odile Eisenstein
- Institut Charles Gerhardt (ICGM)
- UMR 5253
- Univ. Montpellier
- CNRS
- ENSCM
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13
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Sun G, Saw S, Douglass I, Harrowell P. Structural Origin of Enhanced Dynamics at the Surface of a Glassy Alloy. PHYSICAL REVIEW LETTERS 2017; 119:245501. [PMID: 29286748 DOI: 10.1103/physrevlett.119.245501] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Indexed: 06/07/2023]
Abstract
The enhancement of mobility at the surface of an amorphous alloy is studied using a combination of molecular dynamic simulations and normal mode analysis of the nonuniform distribution of Debye-Waller factors. The increased mobility at the surface is found to be associated with the appearance of Arrhenius temperature dependence. We show that the transverse Debye-Waller factor exhibits a peak at the surface. Over the accessible temperature range, we find that the bulk and surface diffusion coefficients obey the same empirical relationship with the respective Debye-Waller factors. Extrapolating this relationship to lower T, we argue that the observed decrease in the constraint at the surface is sufficient to account for the experimentally observed surface enhancement of mobility.
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Affiliation(s)
- Gang Sun
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Shibu Saw
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Ian Douglass
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Peter Harrowell
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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14
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Chen Y, Zhu M, Laventure A, Lebel O, Ediger MD, Yu L. Influence of Hydrogen Bonding on the Surface Diffusion of Molecular Glasses: Comparison of Three Triazines. J Phys Chem B 2017. [PMID: 28651429 DOI: 10.1021/acs.jpcb.7b05333] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Surface grating decay measurements have been performed on three closely related molecular glasses to study the effect of intermolecular hydrogen bonds on surface diffusion. The three molecules are derivatives of bis(3,5-dimethyl-phenylamino)-1,3,5-triazine and differ only in the functional group R at the 2-position, with R being C2H5, OCH3, and NHCH3, and referred to as "Et", "OMe", and "NHMe", respectively. Of the three molecules, NHMe forms more extensive intermolecular hydrogen bonds than Et and OMe and was found to have slower surface diffusion. For Et and OMe, surface diffusion is so fast that it replaces viscous flow as the mechanism of surface grating decay as temperature is lowered. In contrast, no such transition was observed for NHMe under the same conditions, indicating significantly slower surface diffusion. This result is consistent with the previous finding that extensive intermolecular hydrogen bonds slow down surface diffusion in molecular glasses and is attributed to the persistence of hydrogen bonds even in the surface environment. This result is also consistent with the lower stability of the vapor-deposited glass of NHMe relative to those of Et and OMe and supports the view that surface mobility controls the stability of vapor-deposited glasses.
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Affiliation(s)
- Yinshan Chen
- School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Men Zhu
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Audrey Laventure
- Department of Chemistry and Chemical Engineering, Royal Military College of Canada , Kingston, Ontario K7K 7B4, Canada
| | - Olivier Lebel
- Department of Chemistry and Chemical Engineering, Royal Military College of Canada , Kingston, Ontario K7K 7B4, Canada
| | - M D Ediger
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Lian Yu
- School of Pharmacy, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.,Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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15
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Li YZ, Sun YT, Lu Z, Li MZ, Bai HY, Wang WH. Size effect on dynamics and glass transition in metallic liquids and glasses. J Chem Phys 2017; 146:224502. [DOI: 10.1063/1.4984977] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Y. Z. Li
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Y. T. Sun
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Z. Lu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - M. Z. Li
- Department of Physics, Beijing Key Laboratory of Opto-Electronic Functional Materials and Micro-Nano Devices, Renmin University of China, Beijing 100872, China
| | - H. Y. Bai
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - W. H. Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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16
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Ruan S, Zhang W, Sun Y, Ediger MD, Yu L. Surface diffusion and surface crystal growth of tris-naphthyl benzene glasses. J Chem Phys 2016. [DOI: 10.1063/1.4960301] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Shigang Ruan
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Wei Zhang
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | | | - M. D. Ediger
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | - Lian Yu
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
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17
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Chen Y, Zhang W, Yu L. Hydrogen Bonding Slows Down Surface Diffusion of Molecular Glasses. J Phys Chem B 2016; 120:8007-15. [DOI: 10.1021/acs.jpcb.6b05658] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Yinshan Chen
- School of Pharmacy and ‡Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53705, United States
| | - Wei Zhang
- School of Pharmacy and ‡Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53705, United States
| | - Lian Yu
- School of Pharmacy and ‡Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53705, United States
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18
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Varnik F, Franosch T. Non-monotonic effect of confinement on the glass transition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:133001. [PMID: 26940539 DOI: 10.1088/0953-8984/28/13/133001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. This effect has mostly been observed to be a monotonic function of the slit width. Recently, a qualitatively new behaviour has been uncovered by Mittal and coworkers, who reported that the single particle dynamics in a hard-sphere fluid confined in a planar slit varies in a non-monotonic way as the slit width is decreased from five to roughly two particle diametres (Mittal et al 2008 Phys. Rev. Lett. 100 145901). In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g. nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom's insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree of confinement varies with distance from the apex. This is a very promising issue for future research with the possibility of uncovering the existence of alternating glassy and liquid-like domains.
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Affiliation(s)
- Fathollah Varnik
- Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum, Germany
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Rimola A, Ugliengo P, Sodupe M. Strained ring motif at silica surfaces: A quantum mechanical study of their reactivity towards protic molecules. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2015.10.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Kimura H, Wada K, Senshu H, Kobayashi H. COHESION OF AMORPHOUS SILICA SPHERES: TOWARD A BETTER UNDERSTANDING OF THE COAGULATION GROWTH OF SILICATE DUST AGGREGATES. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/812/1/67] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Habasaki J, Ishikawa M. Molecular dynamics study of coagulation in silica-nanocolloid-water-NaCl systems based on the atomistic model. Phys Chem Chem Phys 2014; 16:24000-17. [PMID: 25285911 DOI: 10.1039/c4cp02984d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present work, large scale molecular dynamics (MD) simulations of nanocolloidal silica in aqueous NaCl solutions were performed using a fully atomistic model to study the microscopic structures and dynamics of the systems that lead to aggregation or gelation. Our attention is focused on the self-organizations that occur in the structures of the colloidal silica and water for various concentrations of NaCl. As the salt concentration increased, coagulation developed through the direct bonding of SiO4 units. The trend was explained by the systematic changes in the pair correlation functions related to the barrier height in the potential of mean force [J. G. Kirkwood, J. Chem. Phys., 1935, 3, 300]. Network structures of silica were visualised, and their fractal dimensions were examined by computing the running coordination numbers of Si-Si pairs and also by the analysis of two dimensional images. The calculated dimension by the former method was comparable to the experimental observations for the aggregation of silica colloids, and at longer length scales, super-aggregation was evident in the gelation process. The result from the 2D images is found to be insensitive to the differences in the structure. Clear changes in both the structure and mobility of the water were observed as the NaCl concentration increased, suggesting the importance of the solvent structures to these processes, although such a feature is lacking in the conventional models and most simulations of colloids.
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Affiliation(s)
- Junko Habasaki
- Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8502, Japan.
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Brittle to ductile transition in densified silica glass. Sci Rep 2014; 4:5035. [PMID: 24849328 PMCID: PMC4030258 DOI: 10.1038/srep05035] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 05/02/2014] [Indexed: 11/30/2022] Open
Abstract
Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior.
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Probing of 2 dimensional confinement-induced structural transitions in amorphous oxide thin film. Sci Rep 2014; 4:4200. [PMID: 24569515 PMCID: PMC3935193 DOI: 10.1038/srep04200] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 02/06/2014] [Indexed: 11/08/2022] Open
Abstract
Whereas the atomic structure of surface of crystals is known to be distinct from that of bulk, experimental evidence for thickness-induced structural transitions in amorphous oxides is lacking. We report the NMR result for amorphous alumina with varying thickness from bulk up to 5 nm, revealing the nature of structural transitions near amorphous oxide surfaces/interfaces. The coordination environments in the confined amorphous alumina thin film are distinct from those of bulk, highlighted by a decrease in the fractions of high-energy clusters (and thus the degree of disorder) with thickness. The result implies that a wide range of variations in amorphous structures may be identified by controlling its dimensionality.
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Qomi MJA, Bauchy M, Ulm FJ, Pellenq RJM. Anomalous composition-dependent dynamics of nanoconfined water in the interlayer of disordered calcium-silicates. J Chem Phys 2014; 140:054515. [DOI: 10.1063/1.4864118] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Rimola A, Costa D, Sodupe M, Lambert JF, Ugliengo P. Silica surface features and their role in the adsorption of biomolecules: computational modeling and experiments. Chem Rev 2013; 113:4216-313. [PMID: 23289428 DOI: 10.1021/cr3003054] [Citation(s) in RCA: 328] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Albert Rimola
- Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Cerdanyola del Vallès), Spain
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Landers J, Gor GY, Neimark AV. Density functional theory methods for characterization of porous materials. Colloids Surf A Physicochem Eng Asp 2013. [DOI: 10.1016/j.colsurfa.2013.01.007] [Citation(s) in RCA: 768] [Impact Index Per Article: 69.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Yang K, Lin Y, Lu X, Neimark AV. Solvation forces between molecularly rough surfaces. J Colloid Interface Sci 2011; 362:382-8. [DOI: 10.1016/j.jcis.2011.06.056] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 06/21/2011] [Accepted: 06/23/2011] [Indexed: 11/16/2022]
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Youssef M, Pellenq RJM, Yildiz B. Glassy nature of water in an ultraconfining disordered material: the case of calcium-silicate-hydrate. J Am Chem Soc 2011; 133:2499-510. [PMID: 21294516 DOI: 10.1021/ja107003a] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly disordered calcium-silicate-hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the disordered silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the calcium-silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 Å, a disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 Å, and persisting spatial correlations through dipole-dipole interactions up to 10 Å. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteristic of the dynamics in supercooled liquids and glasses, consistent with its intermediate-range structure identified here. At the intermediate time scales corresponding to the β-relaxation of glassy materials, coincident with the cage stage in MSD, the non-Gaussian parameter indicates a significant heterogeneity in the translational dynamics. This dynamic heterogeneity is induced primarily because of the heterogeneity in the distribution of hydrogen bond strengths. The strongly attractive interactions of water molecules with the calcium silicate walls serve to constrain their motion. Our findings have important implications on describing the cohesion and mechanical behavior of cement from its setting to its aging.
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Affiliation(s)
- Mostafa Youssef
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Chashchikhin V, Rykova E, Bagaturyants A. Density functional theory modeling of the adsorption of small analyte and indicator dye 9-(diphenylamino)acridine molecules on the surface of amorphous silicananoparticles. Phys Chem Chem Phys 2011; 13:1440-7. [DOI: 10.1039/c0cp00821d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Kermode JR, Cereda S, Tangney P, De Vita A. A first principles based polarizable O(N) interatomic force field for bulk silica. J Chem Phys 2010; 133:094102. [DOI: 10.1063/1.3475565] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Hoang VV, Khanh BTHL. Static and thermodynamic properties of liquid and amorphous Fe(2)O(3) nanoparticles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:075103. [PMID: 21817318 DOI: 10.1088/0953-8984/21/7/075103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Molecular dynamics (MD) simulation of the structure and thermodynamic properties of liquid and amorphous Fe(2)O(3) nanoparticles, with different sizes ranging from 2 to 5 nm, has been carried out based on the Born-Mayer pair potentials under non-periodic boundary conditions. The partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances of liquid nanoparticles at 3500 K were calculated in detail. In addition, we show the radial density profile and stoichiometry in nanoparticles. The temperature dependence of the surface structure and surface energy of nanoparticles has been obtained and presented. Moreover, the size dependence of the glass transition temperature has been found and discussed.
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Affiliation(s)
- Vo Van Hoang
- Department of Physics, Institute of Technology, HoChiMinh City National University, 268 Ly Thuong Kiet Street, District 10, HoChiMinh City, Vietnam
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Linh NN, Hoang VV. Surface structure and structural point defects of liquid and amorphous aluminosilicate nanoparticles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:265005. [PMID: 21694354 DOI: 10.1088/0953-8984/20/26/265005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The surface structure of liquid and amorphous aluminosilicate nanoparticles of composition Al(2)O(3)·2SiO(2) has been investigated in a model of different sizes ranging from 2.0 to 5.0 nm with the Born-Mayer type pair potential under non-periodic boundary conditions. Models have been obtained by cooling from the melts at a constant density of 2.6 g cm(-3) via molecular dynamics (MD) simulation. The surface structure has been investigated via the coordination number, bond-angle distributions and structural point defects. Calculations show that surface effects on surface static and thermodynamic properties of models are significant according to the change in the number of Al atoms in the surface layers. Evolution of the local environment of oxygen in the surface shell of nanoparticles upon cooling from the melt toward the glassy state was also found and discussed. In addition, the nanosize dependence of the glass transition temperature was presented.
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Affiliation(s)
- Nguyen Ngoc Linh
- Department of Physics, Institute of Technology, National University of HoChiMinh City, 268 Ly Thuong Kiet Street, District 10, HoChiMinh City, Vietnam
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Lacks DJ, Robinson MP. Mechanical heterogeneity in nanoscale films of liquid silica. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:041504. [PMID: 18517625 DOI: 10.1103/physreve.77.041504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2007] [Indexed: 05/26/2023]
Abstract
Molecular dynamics simulations are carried out for slabs of silica liquid with thicknesses between 1 and 3 nm . A local analysis of the Born contribution to the elastic modulus, CB, shows that the elasticity is not uniform throughout the slabs--CB is identical to that of bulk silica in the slab interior, but CB is larger at the slab edges. The larger CB at the slab edges is due to a distinct atomic level structure characterized by larger density, larger concentration of more highly coordinated ions, and smaller silica rings.
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Affiliation(s)
- Daniel J Lacks
- Department of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Hoang VV. The glass transition and thermodynamics of liquid and amorphous TiO(2) nanoparticles. NANOTECHNOLOGY 2008; 19:105706. [PMID: 21817714 DOI: 10.1088/0957-4484/19/10/105706] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The glass transition and thermodynamics of spherical liquid TiO(2) nanoparticles, with different sizes ranging from 2 to 5 nm, have been studied in a model under non-periodic boundary conditions. We use the pairwise interatomic potentials proposed by Matsui and Akaogi. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. The structural properties of liquid nanoparticles at 3500 K have been analyzed in detail through the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Moreover, we also show the radial density profile in nanoparticles. Calculations show that size effects on the structure of a model are significant and that liquid TiO(2) nanoparticles have a distorted pentahedral network structure with the mean coordination numbers Z(Ti-O)≈5.0 and Z(O-Ti)≈2.5, while amorphous TiO(2) nanoparticles have an octahedral network structure. The temperature dependence of the surface structure and surface energy of the nanoparticles has been obtained and is presented. In addition, the size dependence of the glass transition temperature and the temperature dependence of the diffusion constant of atomic species have been found and are discussed.
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Affiliation(s)
- Vo Van Hoang
- Department of Physics, Institute of Technology, National University of HochiMinh City, 268 Ly Thuong Kiet Street, Distr. 10, HochiMinh City, Vietnam
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Linh N, Hoang V. Structural properties of amorphous Al2O3·2SiO2nanoparticles. MOLECULAR SIMULATION 2008. [DOI: 10.1080/08927020801930521] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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37
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Mahajan SS, Subbarayan G, Sammakia BG. Estimating thermal conductivity of amorphous silica nanoparticles and nanowires using molecular dynamics simulations. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:056701. [PMID: 18233784 DOI: 10.1103/physreve.76.056701] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Revised: 06/24/2007] [Indexed: 05/25/2023]
Abstract
In several recent applications, including those aimed at developing thermal interface materials, nanoparticulate systems have been proposed to improve the effective behavior of the system. While nanoparticles by themselves may have low conductivities relative to larger particles owing to interfacial resistance, their use along with larger particles is believed to enhance the percolation threshold leading to better effective behavior overall. One critical challenge in using nanoparticulate systems is the lack of knowledge regarding their thermal conductivity. In this paper, the thermal conductivity of silica clusters (or nanoparticles) as well as nanowires is determined using molecular dynamics (MD) simulations. The equilibrium MD simulations of nanoparticles using Green-Kubo relations are demonstrated to be computationally very expensive and unsuitable for such nanoscaled systems. A nonequilibrium MD method adapted from the study of Müller-Plathe is shown to be faster and more accurate. The method is first demonstrated on bulk amorphous silica (using both cubic and orthorhombic simulation cells) and silica nanowires. The thermal conductivity values are compared to those reported in the literature. The mean thermal conductivity values for bulk silica and silica nanowire were estimated to be 1.2 W/mK and 1.435 W/mK, respectively. To model nanoparticles, the Müller-Plathe technique is adapted by dividing the cluster into concentric shells so as to capture the naturally radial mode of heat transfer. The mean thermal conductivity value of a 600-atom silica nanoparticle obtained using this approach was 0.589 W/mK. This value is approximately 50-60% lower than those of bulk silica or silica nanowire.
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Affiliation(s)
- Sanket S Mahajan
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907-2088, USA
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Abstract
Molecular dynamics simulation of amorphous SiO2 spherical nanoparticles has been carried out in a model with different sizes, 2, 4, and 6 nm, under non-periodic boundary conditions. We use the pair interatomic potentials which have weak Coulomb interaction and Morse type short-range interaction. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of amorphous nanoparticles obtained at 350 K have been studied via partial radial distribution functions (PRDFs), mean interatomic distances, coordination numbers, and bond-angle distributions, which are compared with those observed in the bulk. Calculations of the radial density profile in nanoparticles show the tendency of oxygen to concentrate at the surface as observed previously in other amorphous clusters or thin films. Size effects on structure of nanosized models are significant. The calculations show that if the size is larger than 4 nm, amorphous SiO2 nanoparticles have a distorted tetrahedral network structure with the mean coordination number ZSi-O approximately 4.0 and ZO-Si approximately 2.0 like those observed in the bulk. Surface structure, surface energy, and glass transition temperature of SiO2 nanoparticles have been obtained and presented.
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Affiliation(s)
- Vo Van Hoang
- Department of Physics, Institute of Technology, National University of HochiMinh City, 268 Ly Thuong Kiet, District 10, HochiMinh City, Vietnam.
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Carré A, Berthier L, Horbach J, Ispas S, Kob W. Amorphous silica modeled with truncated and screened Coulomb interactions: A molecular dynamics simulation study. J Chem Phys 2007; 127:114512. [PMID: 17887862 DOI: 10.1063/1.2777136] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We show that finite-range alternatives to the standard long-range pair potential for silica by van Beest et al. [Phys. Rev. Lett. 64, 1955 (1990)] might be used in molecular dynamics simulations. We study two such models that can be efficiently simulated since no Ewald summation is required. We first consider the Wolf method, where the Coulomb interactions are truncated at a cutoff distance rc such that the requirement of charge neutrality holds. Various static and dynamic quantities are computed and compared to results from simulations using Ewald summations. We find very good agreement for rc approximately 10 A. For lower values of rc, the long-range structure is affected which is accompanied by a slight acceleration of dynamic properties. In a second approach, the Coulomb interaction is replaced by an effective Yukawa interaction with two new parameters determined by a force fitting procedure. The same trend as for the Wolf method is seen. However, slightly larger cutoffs have to be used in order to obtain the same accuracy with respect to static and dynamic quantities as for the Wolf method.
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Affiliation(s)
- Antoine Carré
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55099 Mainz, Germany
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Hassanali AA, Singer SJ. Model for the Water−Amorphous Silica Interface: The Undissociated Surface. J Phys Chem B 2007; 111:11181-93. [PMID: 17803296 DOI: 10.1021/jp062971s] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The physical and chemical properties of the amorphous silica-water interface are of crucial importance for a fundamental understanding of electrochemical and electrokinetic phenomena, and for various applications including chromatography, sensors, metal ion extraction, and the construction of micro- and nanoscale devices. A model for the undissociated amorphous silica-water interface reported here is a step toward a practical microscopic model of this important system. We have extended the popular BKS and SPC/E models for bulk silica and water to describe the hydrated, hydroxylated amorphous silica surface. The parameters of our model were determined using ab initio quantum chemical studies on small fragments. Our model will be useful in empirical potential studies, and as a starting point for ab initio molecular dynamics calculations. At this stage, we present a model for the undissociated surface. Our calculated value for the heat of immersion, 0.3 J x m(-2), falls within the range of reported experimental values of 0.2-0.8 J x m(-2). We also study the perturbation of water properties near the silica-water interface. The disordered surface is characterized by regions that are hydrophilic and hydrophobic, depending on the statistical variations in silanol group density.
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Affiliation(s)
- Ali A Hassanali
- Biophysics Program and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, USA
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41
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Static and dynamic properties of the water/amorphous silica interface: a model for the undissociated surface. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s10820-006-9038-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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42
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Ravikovitch PI, Neimark AV. Density functional theory model of adsorption on amorphous and microporous solids. STUDIES IN SURFACE SCIENCE AND CATALYSIS 2007. [DOI: 10.1016/s0167-2991(07)80003-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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43
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Ravikovitch PI, Neimark AV. Density functional theory model of adsorption on amorphous and microporous silica materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:11171-9. [PMID: 17154599 DOI: 10.1021/la0616146] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We present a novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity. Within QSDFT, solid atoms are considered as quenched component(s) of the solid-fluid system with given density distribution(s). Solid-fluid intermolecular interactions are split into hard-sphere repulsive and mean-field attractive parts. The former are treated with the multicomponent fundamental measure density functional. Capabilities of QSDFT are demonstrated by drawing on the example of adsorption on amorphous silica materials. We show that, using established intermolecular potentials and a realistic model for silica surfaces, QSDFT quantitatively describes adsorption/desorption isotherms of Ar and Kr on reference MCM-41, SBA-15, and LiChrosphere materials in a wide range of relative pressures. QSDFT offers a systematic approach to the practical problems of characterization of microporous, mesoporous, and amorphous silica materials, including an assessment of microporosity, surface roughness, and adsorption deformation. Predictions for the pore diameter and the extent of pore surface roughness in MCM-41 and SBA-15 materials are in very good agreement with recent X-ray diffraction studies.
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Affiliation(s)
- Peter I Ravikovitch
- Center for Modeling and Characterization of Nanoporous Materials, TRI/Princeton, 601 Prospect Avenue, Princeton, NJ 08540, USA.
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44
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Zhang RQ, Fan WJ. Structures and Properties of Silicon Oxide Clusters by Theoretical Investigations. J CLUST SCI 2006. [DOI: 10.1007/s10876-006-0087-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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45
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Xu Q, Sharp ID, Yuan CW, Yi DO, Liao CY, Glaeser AM, Minor AM, Beeman JW, Ridgway MC, Kluth P, Ager JW, Chrzan DC, Haller EE. Large melting-point hysteresis of Ge nanocrystals embedded in SiO2. PHYSICAL REVIEW LETTERS 2006; 97:155701. [PMID: 17155336 DOI: 10.1103/physrevlett.97.155701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Indexed: 05/12/2023]
Abstract
The melting behavior of Ge nanocrystals embedded within SiO2 is evaluated using in situ transmission electron microscopy. The observed melting-point hysteresis is large (+/-17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.
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Affiliation(s)
- Q Xu
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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Zhang D, Zhang RQ. Silica Nanoarchitectures with Tailored Pores Based on the Hybrid Three- and Four-Membered Rings. J Phys Chem B 2006; 110:15269-74. [PMID: 16884244 DOI: 10.1021/jp062103v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inspired by the recent developments in the controlled synthesis of porous materials, we present herein the structural prediction of silica nanoarchitectures by using the three- (3MRs) and four-membered rings (4MRs), which are more frequently found in the nanometer-sized particles than in the bulk form, as building blocks. The proposed models include the active molecular rings, thin nanowires, hollow nanotubes, discrete fullerene-like cages, and porous zeolite-like three-dimensional networks. Their geometrical and electronic structures and properties were studied by performing density functional calculations. These silica nanostructures were proved, using molecular dynamics simulations, to possess intrinsic structural stabilities with highly symmetrical geometries and regular nanochannels. These atomically well-defined clusters, (SiO)(n), are chemically more reactive than those proposed earlier and are energetically more favorable for n > 20 in high-level density functional calculations over the corresponding two-membered ring (2MR) chains and rings as well as the pure 3MR networks. The nanoparticles and nanodevices based on them are expected to have potential technological applications that mainly make use of their characteristic geometrical structures (nanosized pores) and novel electronic properties.
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Affiliation(s)
- Dongju Zhang
- Center of Super-Diamond and Advanced Films and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China
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Electron spin resonance probing of E′-type defects in fumed silica nanoparticles. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2006. [DOI: 10.1016/j.msec.2005.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Zhang D, Zhang RQ. Structural Model of Silica Nanowire Assembled from a Highly Stable (SiO2)8 Unit. J Phys Chem B 2005; 110:1338-43. [PMID: 16471683 DOI: 10.1021/jp052643c] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ground-state structures of silica clusters (SiO2)n for n = 1-8 were studied by performing calculations at the B3LYP/6-311+G(d) level of density functional theory. The results indicate that the growth mode of a silica nanowire based on small silica clusters may change at different wire lengths. A linear chain might be assembled from the smallest clusters of rhombic two-membered ring (2MR) with n < or = 5, while the growth motif changes at n = 6 into a more compact form composed of three-membered-rings (3MRs). The 3MR-containing structures become energetically favorable configurations for even longer silica clusters. In particular, the closed molecular ring consisting of 3MRs at n = 8 (i.e., (SiO2)8) with a high symmetry shows extreme energetic stability and relatively high chemical reactivity and thus is considered to be an important building block to assemble into silica nanowires. The relative stability of so-assembled silica nanowires were evaluated and compared with the models of silica nanowires in the literature.
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Affiliation(s)
- Dongju Zhang
- Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China
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Krüger T, Amkreutz M, Schiffels P, Schneider B, Hennemann OD, Frauenheim T. Theoretical Study of the Interaction between Selected Adhesives and Oxide Surfaces. J Phys Chem B 2005; 109:5060-6. [PMID: 16863166 DOI: 10.1021/jp0448651] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigate the competition of the various organic components of two representative adhesive systems for reactive defect sites at model surfaces of both SiO2 and Al2O3. The reaction energies of resin monomers, curing agents, and in some cases also of additional adhesion promoters with the defects are calculated. We applied a density-functional based tight-binding method including a self-consistent correction of the Mulliken charges, which has already proven to be a useful tool for computational materials science, delivering reliable structural and energetic information.
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Affiliation(s)
- Thomas Krüger
- Theoretical Physics, Faculty of Science, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany.
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Zhang D, Zhao M, Zhang RQ. Two- and Three-Membered-Ring Hybrid Structures of Silica Nanoclusters. J Phys Chem B 2004. [DOI: 10.1021/jp0469620] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dongju Zhang
- Department of Physics and Materials Sciences, City University of Hong Kong, Hong Kong SAR, China
| | - Mingwen Zhao
- Department of Physics and Materials Sciences, City University of Hong Kong, Hong Kong SAR, China
| | - R. Q. Zhang
- Department of Physics and Materials Sciences, City University of Hong Kong, Hong Kong SAR, China
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