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Bellido-Peralta R, Leoni F, Calero C, Franzese G. Size-Pore-Dependent Methanol Sequestration from Water-Methanol Mixtures by an Embedded Graphene Slit. Molecules 2023; 28:molecules28093697. [PMID: 37175107 PMCID: PMC10179872 DOI: 10.3390/molecules28093697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/17/2023] [Accepted: 04/19/2023] [Indexed: 05/15/2023] Open
Abstract
The separation of liquid mixture components is relevant to many applications-ranging from water purification to biofuel production-and is a growing concern related to the UN Sustainable Development Goals (SDGs), such as "Clean water and Sanitation" and "Affordable and clean energy". One promising technique is using graphene slit-pores as filters, or sponges, because the confinement potentially affects the properties of the mixture components in different ways, favoring their separation. However, no systematic study has shown how the size of a pore changes the thermodynamics of the surrounding mixture. Here, we focus on water-methanol mixtures and explore, using Molecular Dynamics simulations, the effects of a graphene pore, with size ranging from 6.5 to 13 Å, for three compositions: pure water, 90%-10%, and 75%-25% water-methanol. We show that tuning the pore size can change the mixture pressure, density and composition in bulk due to the size-dependent methanol sequestration within the pore. Our results can help in optimizing the graphene pore size for filtering applications.
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Affiliation(s)
- Roger Bellido-Peralta
- Secció de Física Estadística i Interdisciplinària, Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - Fabio Leoni
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Carles Calero
- Secció de Física Estadística i Interdisciplinària, Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Giancarlo Franzese
- Secció de Física Estadística i Interdisciplinària, Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
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2
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Hubman A, Urbic T. Structure and thermodynamics of a 2D Lennard-Jones hexagonal fluid. MOLECULAR SIMULATION 2022; 48:1435-1444. [PMID: 37727614 PMCID: PMC10508885 DOI: 10.1080/08927022.2022.2096219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 06/20/2022] [Indexed: 10/17/2022]
Abstract
The thermodynamic and structural properties of the 2D hexagonal soft-sites fluid are examined by integral equation theory benchmarked against extensive Monte Carlo simulations. Hexamers are built of six equal Lennard-Jones segments. Site-site integral equation theory is used to compute site-site correlation functions, excess internal energies and isotherms over a wide range of conditions and compared with results obtained from Monte Carlo simulations. Various approaches for computing the pressure are discussed as well. Satisfactory qualitative agreement between theory and simulations is found with details depending on the applied closure relation.
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Affiliation(s)
- Anže Hubman
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Tomaz Urbic
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
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3
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Munguía-Valadez J, Chávez-Rojo MA, Sambriski EJ, Moreno-Razo JA. The generalized continuous multiple step (GCMS) potential: model systems and benchmarks. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:184002. [PMID: 35090143 DOI: 10.1088/1361-648x/ac4fe8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
The generalized continuous multiple step (GCMS) potential is presented in this work. Its flexible form allows forrepulsiveand/orattractivecontributions to be encoded through adjustable energy and length scales. The GCMS interaction provides a continuous representation of square-well, square-shoulder potentials and their variants for implementation in computer simulations. A continuous and differentiable energy representation is required to derive forces in conventional simulation algorithms. Molecular dynamics simulations are of particular interest when considering the dynamic properties of a system. The GCMS potential can mimic other interactions with a judicious choice of parameters due to the versatile sigmoid form. In this study, our benchmarks for the GCMS representation include triangular, Yukawa, Franzese, and Lennard-Jones potentials. Comparisons made with published data on volumetric phase diagrams, liquid structure, and diffusivity from model systems are in excellent agreement.
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Affiliation(s)
- Jorge Munguía-Valadez
- Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Avenida San Rafael Atlixco No. 186, Colonia Vicentina, Delegación Iztapalapa, Mexico City 09340 Mexico
| | - Marco Antonio Chávez-Rojo
- Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito Universitario s/n, Campus II, Chihuahua, Chihuahua 31125, Mexico
| | - Edward John Sambriski
- Department of Chemistry, Delaware Valley University, 700 East Butler Avenue, Doylestown, PA 18901 United States of America
| | - José Antonio Moreno-Razo
- Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Avenida San Rafael Atlixco No. 186, Colonia Vicentina, Delegación Iztapalapa, Mexico City 09340 Mexico
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4
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Leoni F, Calero C, Franzese G. Nanoconfined Fluids: Uniqueness of Water Compared to Other Liquids. ACS NANO 2021; 15:19864-19876. [PMID: 34807577 PMCID: PMC8717635 DOI: 10.1021/acsnano.1c07381] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 11/18/2021] [Indexed: 05/27/2023]
Abstract
Nanoconfinement can drastically change the behavior of liquids, puzzling us with counterintuitive properties. It is relevant in applications, including decontamination and crystallization control. However, it still lacks a systematic analysis for fluids with different bulk properties. Here we address this gap. We compare, by molecular dynamics simulations, three different liquids in a graphene slit pore: (1) A simple fluid, such as argon, described by a Lennard-Jones potential; (2) an anomalous fluid, such as a liquid metal, modeled with an isotropic core-softened potential; and (3) water, the prototypical anomalous liquid, with directional HBs. We study how the slit-pore width affects the structure, thermodynamics, and dynamics of the fluids. All the fluids show similar oscillating properties by changing the pore size. However, their free-energy minima are quite different in nature: (i) are energy-driven for the simple liquid; (ii) are entropy-driven for the isotropic core-softened potential; and (iii) have a changing nature for water. Indeed, for water, the monolayer minimum is entropy driven, at variance with the simple liquid, while the bilayer minimum is energy driven, at variance with the other anomalous liquid. Also, water has a large increase in diffusion for subnm slit pores, becoming faster than bulk. Instead, the other two fluids have diffusion oscillations much smaller than water, slowing down for decreasing slit-pore width. Our results, clarifying that water confined at the subnm scale behaves differently from other (simple or anomalous) fluids under similar confinement, are possibly relevant in nanopores applications, for example, in water purification from contaminants.
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Affiliation(s)
- Fabio Leoni
- Department
of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Carles Calero
- Secció
de Física Estadística i Interdisciplinària-Departament
de Física de la Matèria Condensada, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat
de Barcelona, Carrer Martí i Franquès 1, 08028 Barcelona, Spain
| | - Giancarlo Franzese
- Secció
de Física Estadística i Interdisciplinària-Departament
de Física de la Matèria Condensada, Institut de Nanociència i Nanotecnologia (IN2UB), Universitat
de Barcelona, Carrer Martí i Franquès 1, 08028 Barcelona, Spain
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5
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Marques MS, Hernandes VF, Bordin JR. Core-softened water-alcohol mixtures: the solute-size effects. Phys Chem Chem Phys 2021; 23:16213-16223. [PMID: 34304261 DOI: 10.1039/d1cp00751c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Water is the most anomalous material on Earth, with a long list of thermodynamic, dynamic and structural behaviors that deviate from what is expected. Recent studies have indicated that these anomalies may be related to a competition between two liquids, which means that water has a potential liquid-liquid phase transition (LLPT) that ends at a liquid-liquid critical point (LLCP). In a recent study [J. Mol. Liq., 2020, 320, 114420], using molecular dynamics simulations and a core-softened potential approach, we have shown that adding a simple solute such as methanol can "kill" the density-anomalous behavior as the LLCP is suppressed by spontaneous crystallization in a hexagonal close packing (HCP) crystal near the LLPT. Now, we extend this work to realize how longer-chain alcohols will affect the complex behavior of water-alcohol mixtures in the supercooled regime. Besides core-softened (CS) methanol, ethanol and 1-propanol were added to a system of identical particles that interact through the continuous shouldered well (CSW) potential. We observed that the density anomaly gradually decreases its extension in phase diagrams until it disappears with the growth of the non-polar chain and the alcohol concentration, different from the liquid-liquid phase transition (and the LLCP), which remained present in all analyzed mixtures, according to Nature, 2001, 409, 692. For our model, the longer non-polar chains and higher concentrations gradually impact the competition between the scales in the CS potential, leading to a gradual disappearing of the anomalies until the TMD total disappearance is observed when the first coordination shell structure is also affected: short-range ordering is favored, leading to less competition between short- and long-range ordering and, consequently, to the extinction of anomalies. Also, the non-polar chain size and concentration have an effect on the solid phases, favoring the hexagonal close packed (HCP) solid and the amorphous solid phase over the body-centered cubic (BCC) crystal. These findings help to elucidate the behavior of water solutions in the supercooled regime and indicate that the LLCP can be observed in systems without density-anomalous behavior.
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Affiliation(s)
- Murilo S Marques
- Centro das Ciências Exatas e das Tecnologias, Universidade Federal do Oeste da Bahia, Rua da Prainha, 1392, Morada Nobre, CEP 47810-059, Barreiras-BA, Brazil.
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7
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Hostnik G, Podlipnik Č, Mériguet G, Cerar J. Specificity of Counterion Binding to a Conjugated Polyelectrolyte: A Combined Molecular Dynamics and NOESY Investigation. Macromolecules 2020; 53:1119-1128. [PMID: 32587418 PMCID: PMC7307957 DOI: 10.1021/acs.macromol.9b02161] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/11/2019] [Indexed: 02/06/2023]
Abstract
Poly(thiophen-3-ylacetic acid) (PTAA) is a representative of conjugated polyelectrolytes which are used in many optoelectronics devices. The performance of these devices is affected by the polymer conformation, which, among others, depends on the nature of the counterion. In this study, the binding of tetrabutylammonium counterions (TBA+) on PTAA was determined using a combination of nuclear Overhauser effect spectroscopy (NOESY) and molecular dynamics (MD) simulation. It was found that TBA+ ions specifically bind on the hydrophobic main chain of PTAA, while, according to MD simulations, alkali counterions predominantly bind in the vicinity of negatively charged carboxylic groups located on side chains. The MD trajectories were used to compute the relaxation matrices and the NOESY spectra. With the help of these latter calculations, the changes of intensities in experimental NOESY spectra upon binding of TBA+ ions to PTAA were interpreted.
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Affiliation(s)
- Gregor Hostnik
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna Pot 113, SI-1000 Ljubljana, Slovenia
- Faculty
of Chemistry and Chemical Technology, University
of Maribor, SI-2000 Maribor, Slovenia
| | - Črtomir Podlipnik
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna Pot 113, SI-1000 Ljubljana, Slovenia
| | - Guillaume Mériguet
- Sorbonne
Université, CNRS, Laboratoire PHENIX, 4 Place Jussieu, F-75005 Paris, France
| | - Janez Cerar
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna Pot 113, SI-1000 Ljubljana, Slovenia
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8
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de Haro ML, Rodríguez-Rivas Á, Yuste SB, Santos A. Structural properties of the Jagla fluid. Phys Rev E 2018; 98:012138. [PMID: 30110748 DOI: 10.1103/physreve.98.012138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Indexed: 06/08/2023]
Abstract
The structural properties of the Jagla fluid are studied by Monte Carlo (MC) simulations, numerical solutions of integral equation theories, and the (semi-analytical) rational-function approximation (RFA) method. In the latter case, the results are obtained from the assumption (supported by our MC simulations) that the Jagla potential and a potential with a hard core plus an appropriate piecewise constant function lead to practically the same cavity function. The predictions obtained for the radial distribution function, g(r), from this approach are compared against MC simulations and integral equations for the Jagla model, and also for the limiting cases of the triangle-well potential and the ramp potential, with a general good agreement. The analytical form of the RFA in Laplace space allows us to describe the asymptotic behavior of g(r) in a clean way and compare it with MC simulations for representative states with oscillatory or monotonic decay. The RFA predictions for the Fisher-Widom and Widom lines of the Jagla fluid are obtained.
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Affiliation(s)
- Mariano López de Haro
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México (U.N.A.M.), Temixco, Morelos 62580, Mexico
| | - Álvaro Rodríguez-Rivas
- Departamento de Física and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, Badajoz E-06006, Spain
| | - Santos B Yuste
- Departamento de Física and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, Badajoz E-06006, Spain
| | - Andrés Santos
- Departamento de Física and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, Badajoz E-06006, Spain
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9
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Calculating free energy profiles using entropy as a reaction coordinate: Application to water nucleation. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.02.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Leoni F, Franzese G. Effects of confinement between attractive and repulsive walls on the thermodynamics of an anomalous fluid. Phys Rev E 2016; 94:062604. [PMID: 28085471 DOI: 10.1103/physreve.94.062604] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Indexed: 06/06/2023]
Abstract
We study via molecular-dynamics simulations the thermodynamics of an anomalous fluid confined in a slit pore with one wall structured and attractive and another unstructured and repulsive. We find that the phase diagram of the homogeneous part of the confined fluid is shifted to higher temperatures, densities, and pressures with respect to the bulk, but it can be rescaled on the bulk case. We calculate a moderate increase of mobility of the homogeneous confined fluid that we interpret as a consequence of the layering due to confinement and the collective modes due to long-range correlations. We show that, as in bulk, the confined fluid has structural, diffusion, and density anomalies that order in the waterlike hierarchy, and a liquid-liquid critical point (LLCP). The overall anomalous region moves to higher temperatures, densities, and pressure, and the LLCP displaces to higher temperature compared to bulk. Motivated by experiments, we calculate also the phase diagram not just for the homogeneous part of the confined fluid but for the entire fluid in the pore, and we show that it is shifted toward higher pressures but preserves the thermodynamics, including the LLCP. Because our model has waterlike properties, we argue that in experiments with supercooled water confined in slit pores with a width of >3 nm if hydrophilic and of >1.5 nm if hydrophobic, the existence of the LLCP could be easier to test than in bulk, where it is not directly accessible.
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Affiliation(s)
- Fabio Leoni
- Secció de Fisica Estadística i Interdisciplinària-Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, Barcelona 08028, Spain
| | - Giancarlo Franzese
- Secció de Fisica Estadística i Interdisciplinària-Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnología, Universitat de Barcelona, Av. Joan XXIII S/N, Barcelona 08028, Spain
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11
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Urbic T. Properties of the two-dimensional heterogeneous Lennard-Jones dimers: An integral equation study. J Chem Phys 2016; 145:194503. [PMID: 27875894 PMCID: PMC5116027 DOI: 10.1063/1.4967807] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/02/2016] [Indexed: 11/14/2022] Open
Abstract
Structural and thermodynamic properties of a planar heterogeneous soft dumbbell fluid are examined using Monte Carlo simulations and integral equation theory. Lennard-Jones particles of different sizes are the building blocks of the dimers. The site-site integral equation theory in two dimensions is used to calculate the site-site radial distribution functions and the thermodynamic properties. Obtained results are compared to Monte Carlo simulation data. The critical parameters for selected types of dimers were also estimated and the influence of the Lennard-Jones parameters was studied. We have also tested the correctness of the site-site integral equation theory using different closures.
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Affiliation(s)
- Tomaz Urbic
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Vecna pot 113, 1000 Lubljana, Slovenia
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12
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Torres-Carbajal A, Castañeda-Priego R. Characterisation of the thermodynamics, structure and dynamics of a water-like model in 2- and 3-dimensions. Phys Chem Chem Phys 2016; 18:17335-40. [PMID: 27232761 DOI: 10.1039/c6cp01565d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The physical properties of colloidal particles suspended in an aqueous environment are well-understood when the latter is considered to be a continuum and a structureless medium. However, this approach fails to explain complex phenomena, for example, the critical Casimir forces among colloids and the colloidal self-assembly near critical solvents, and the inertial contribution of the solvent molecules on the diffusion of non-spherical Brownian particles. Therefore, the role played by the solvent on the physical properties of colloidal dispersions is of paramount relevance. Recently, there has been an interest in the (non-trivial) diffusion mechanisms of a nano-colloidal particle in a solvent that undergoes a vapour-liquid transition. Nonetheless, the models typically used to incorporate the solvent details do not capture quantitatively the thermodynamic properties of real substances. It is then important to study the Brownian motion of colloids in more realistic models. To reach such goal, one first has to characterise the thermodynamic states and the microscopic features of the solvent. Hence, in this contribution, we have investigated the coexistence densities of a core-softened potential in two- and three-dimensions, whose potential parameters are able to capture some anomalies of water. We show that in the two-dimensional case, the potential model exhibits, besides the normal vapour-liquid coexistence region, additional liquid-liquid coexistence densities. We particularly focus our attention to the structural properties and the dynamical behaviour of the solvent around the liquid-liquid critical point and assess the differences with the three-dimensional case.
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Affiliation(s)
- Alexis Torres-Carbajal
- División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, México.
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13
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Munaò G, Urbic T. Structure and thermodynamics of core-softened models for alcohols. J Chem Phys 2015; 142:214508. [DOI: 10.1063/1.4922164] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Gianmarco Munaò
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Tomaz Urbic
- Department of Chemistry and Chemical Technology, Chair of Physical Chemistry, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
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14
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Abramo MC, Caccamo C, Costa D, Giaquinta PV, Malescio G, Munaò G, Prestipino S. On the determination of phase boundaries via thermodynamic integration across coexistence regions. J Chem Phys 2015; 142:214502. [DOI: 10.1063/1.4921884] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Maria Concetta Abramo
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Carlo Caccamo
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Dino Costa
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Paolo V. Giaquinta
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Gianpietro Malescio
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Gianmarco Munaò
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
| | - Santi Prestipino
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Contrada Papardo, I-98166 Messina, Italy
- CNR-IPCF, Viale F. Stagno d’Alcontres 37, I-98158 Messina, Italy
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15
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Jirsák J, Škvor J. A molecular-based approach to the thermodynamics of aqueous solutions: binary mixture of water and carbon dioxide. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:194114. [PMID: 25923412 DOI: 10.1088/0953-8984/27/19/194114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A simple model and theory of molecular fluids is applied to a binary mixture of water and carbon dioxide. An approach based on the perturbation theory is followed using a reference system of so-called pseudo-hard bodies for water and hard triatomics for carbon dioxide. Pseudo-hard bodies bear the traits of the non-additive nature of association supplementing the common excluded volume effect. The reference term is parametrized using Monte Carlo simulation data on the compressibility factor. After adding a simple mean-field term to the reference equation, fluid phase equilibria are qualitatively reproduced.
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Affiliation(s)
- J Jirsák
- Faculty of Science, J E Purkinje University, České mládeže 8, 400 96 Ústí nad Labem, Czech Republic
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16
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Lobanova O, Avendaño C, Lafitte T, Müller EA, Jackson G. SAFT-γ force field for the simulation of molecular fluids: 4. A single-site coarse-grained model of water applicable over a wide temperature range. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1004804] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Cervantes LA, Jaime-Muñoz G, Benavides AL, Torres-Arenas J, Sastre F. Discrete perturbation theory for continuous soft-core potential fluids. J Chem Phys 2015; 142:114501. [DOI: 10.1063/1.4909550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- L. A. Cervantes
- Departamento de Infraestructura, Universidad de Guanajuato, Noria Alta, Guanajuato, CP 36000, México
| | - G. Jaime-Muñoz
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, Colonia Lomas del Campestre, León, Guanajuato, CP 37150, México
| | - A. L. Benavides
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, Colonia Lomas del Campestre, León, Guanajuato, CP 37150, México
| | - J. Torres-Arenas
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, Colonia Lomas del Campestre, León, Guanajuato, CP 37150, México
| | - F. Sastre
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, Colonia Lomas del Campestre, León, Guanajuato, CP 37150, México
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18
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Huš M, Urbic T. Existence of a liquid-liquid phase transition in methanol. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:062306. [PMID: 25615092 DOI: 10.1103/physreve.90.062306] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Indexed: 06/04/2023]
Abstract
A simple model is constructed to study the phase diagram and thermodynamic properties of methanol, which is described as a dimer of an apolar sphere mimicking the methyl group and a sphere with core-softened potential as the hydroxyl group. Performing classical Monte Carlo simulations, we obtained the phase diagram, showing a second critical point between two different liquid phases. Evaluating systems with a different number of particles, we extrapolate to infinite size in accordance with Ising universality class to obtain bulk values for critical temperature, pressure, and density. Strong evidence that the structure of the liquid changes upon transition from high- to low-density phase was provided. From the experimentally determined hydrogen bond strength and length in methanol and water, we propose where the second critical point of methanol should be.
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Affiliation(s)
- Matej Huš
- Chair of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Tomaz Urbic
- Chair of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
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Huš M, Munaò G, Urbic T. Properties of a soft-core model of methanol: an integral equation theory and computer simulation study. J Chem Phys 2014; 141:164505. [PMID: 25362323 DOI: 10.1063/1.4899316] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thermodynamic and structural properties of a coarse-grained model of methanol are examined by Monte Carlo simulations and reference interaction site model (RISM) integral equation theory. Methanol particles are described as dimers formed from an apolar Lennard-Jones sphere, mimicking the methyl group, and a sphere with a core-softened potential as the hydroxyl group. Different closure approximations of the RISM theory are compared and discussed. The liquid structure of methanol is investigated by calculating site-site radial distribution functions and static structure factors for a wide range of temperatures and densities. Results obtained show a good agreement between RISM and Monte Carlo simulations. The phase behavior of methanol is investigated by employing different thermodynamic routes for the calculation of the RISM free energy, drawing gas-liquid coexistence curves that match the simulation data. Preliminary indications for a putative second critical point between two different liquid phases of methanol are also discussed.
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Affiliation(s)
- Matej Huš
- Department of Chemistry and Chemical Technology, University of Ljubljana, Chair of Physical Chemistry, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Gianmarco Munaò
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy
| | - Tomaz Urbic
- Department of Chemistry and Chemical Technology, University of Ljubljana, Chair of Physical Chemistry, Večna pot 113, SI-1000 Ljubljana, Slovenia
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Huš M, Urbic T. Thermodynamics and the hydrophobic effect in a core-softened model and comparison with experiments. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:022115. [PMID: 25215697 DOI: 10.1103/physreve.90.022115] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Indexed: 06/03/2023]
Abstract
A simple and computationally inexpensive core-softened model, originally proposed by Franzese [G. Franzese, J. Mol. Liq. 136, 267 (2007)], was adopted to show that it exhibits properties of waterlike fluid and hydrophobic effect. The potential used between particles is spherically symmetric with two characteristic lengths. Thermodynamics of nonpolar solvation were modeled as an insertion of a modified Lennard-Jones particle. It was investigated how the anomalous predictions of the model as well as the nonpolar solvation compare with the experimental data for water anomalies and the temperature dependence of noble gases hydration. It was shown that the model qualitatively follows the same trends as water. The model is able to reproduce waterlike anomalous properties (density maximum, heat capacity minimum, isothermal compressibility, etc.) and hydrophobic effect (minimum solubility for nonpolar solutes near ambient conditions, increased solubility of larger noble gases, etc.). It is argued that the model yields similar results as more complex and computationally expensive models.
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Affiliation(s)
- Matej Huš
- University of Ljubljana, Department of Chemistry and Chemical Technology, Chair of Physical Chemistry, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
| | - Tomaz Urbic
- University of Ljubljana, Department of Chemistry and Chemical Technology, Chair of Physical Chemistry, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
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Huš M, Urbic T. The hydrophobic effect in a simple isotropic water-like model: Monte Carlo study. J Chem Phys 2014; 140:144904. [PMID: 24735315 DOI: 10.1063/1.4870514] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Using Monte Carlo computer simulations, we show that a simple isotropic water-like model with two characteristic lengths can reproduce the hydrophobic effect and the solvation properties of small and large non-polar solutes. Influence of temperature, pressure, and solute size on the thermodynamic properties of apolar solute solvation in a water model was systematically studied, showing two different solvation regimes. Small particles can fit into the cavities around the solvent particles, inducing additional order in the system and lowering the overall entropy. Large particles force the solvent to disrupt their network, increasing the entropy of the system. At low temperatures, the ordering effect of small solutes is very pronounced. Above the cross-over temperature, which strongly depends on the solute size, the entropy change becomes strictly positive. Pressure dependence was also investigated, showing a "cross-over pressure" where the entropy and enthalpy of solvation are the lowest. These results suggest two fundamentally different solvation mechanisms, as observed experimentally in water and computationally in various water-like models.
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Affiliation(s)
- Matej Huš
- Chair of Physical Chemistry, Department of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
| | - Tomaz Urbic
- Chair of Physical Chemistry, Department of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
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Almudallal AM, Buldyrev SV, Saika-Voivod I. Inverse melting in a two-dimensional off-lattice model. J Chem Phys 2014; 140:144505. [DOI: 10.1063/1.4870086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Urbic T, Dias CL. Properties of the Lennard-Jones dimeric fluid in two dimensions: an integral equation study. J Chem Phys 2014; 140:094703. [PMID: 24606372 PMCID: PMC3977749 DOI: 10.1063/1.4867289] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 02/19/2014] [Indexed: 12/21/2022] Open
Abstract
The thermodynamic and structural properties of the planar soft-sites dumbbell fluid are examined by Monte Carlo simulations and integral equation theory. The dimers are built of two Lennard-Jones segments. Site-site integral equation theory in two dimensions is used to calculate the site-site radial distribution functions for a range of elongations and densities and the results are compared with Monte Carlo simulations. The critical parameters for selected types of dimers were also estimated. We analyze the influence of the bond length on critical point as well as tested correctness of site-site integral equation theory with different closures. The integral equations can be used to predict the phase diagram of dimers whose molecular parameters are known.
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Affiliation(s)
- Tomaz Urbic
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
| | - Cristiano L Dias
- Physics Department, New Jersey Institute of Technology, Newark, New Jersey 07102-1982, USA
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