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Mazzilli V, Satoh K, Saielli G. Phase behaviour of mixtures of charged soft disks and spheres. SOFT MATTER 2023; 19:3311-3324. [PMID: 37093590 DOI: 10.1039/d3sm00223c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We have investigated the phase behaviour of mixtures of soft disks (Gay-Berne oblate ellipsoids, GB) and soft spheres (Lennard-Jones, LJ) with opposite charge as a model of ionic liquid crystals and colloidal suspensions. We have used constant volume Molecular Dynamics simulations and fixed the stoichiometry of the mixture in order to have electroneutrality; three systems have been selected GB : LJ = 1 : 2, GB : LJ = 1 : 1 and GB : LJ = 2 : 1. For each system we have selected three values of the scaled point charge q* of the GB particles, namely 0.5, 1.0 and 2.0 (and a corresponding negative scaled charge of the LJ particles that depends on the stoichiometric ratio). We have found a very rich mesomorphism with the formation, as a function of the scaled temperature, of the isotropic phase, the discotic nematic phase, the hexagonal columnar phase and crystal phases. While the structure of the high temperature phases was similar in all systems, the hexagonal columnar phases exhibited a highly variable morphology depending on the scaled charge and stoichiometry. On the one hand, GB : LJ = 1 : 2 systems form lamellar structures, akin to smectic phases, with an alternation of layers of disks (exhibiting an hexagonal columnar phase) and layers of LJ particles (in the isotropic phase). On the other hand, for the 2 : 1 stoichiometry we observe the formation of a frustrated hexagonal columnar phase with an alternating tilt direction of the molecular axis. We rationalize these findings based on the structure of the neutral ion pair dominating the behaviour at low temperature and high charge.
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Affiliation(s)
- Valerio Mazzilli
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
- CNR-ITM, Institute on Membrane Technology, Padova Unit, Via Marzolo, 1, 35131 Padova, Italy
| | - Katsuhiko Satoh
- Department of Chemistry, Osaka Sangyo University, Daito, Osaka, 574-8530, Japan.
| | - Giacomo Saielli
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
- CNR-ITM, Institute on Membrane Technology, Padova Unit, Via Marzolo, 1, 35131 Padova, Italy
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Perini G, Avendaño C, Hicks W, Parsons AR, Vetter T. Predicting filtration of needle-like crystals: A Monte Carlo simulation study of polydisperse packings of spherocylinders. Chem Eng Sci 2021. [DOI: 10.1016/j.ces.2020.116151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Chávez-Navarro MA, González-Tovar E, Chávez-Páez M. Enhanced charge reversal and charge amplification in a shape- and size-asymmetric electric double layer: the effect of big ions. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1791368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- M. A. Chávez-Navarro
- Instituto de Física, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - E. González-Tovar
- Instituto de Física, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - M. Chávez-Páez
- Instituto de Física, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
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4
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Affiliation(s)
- Michael P. Allen
- Department of Physics, University of Warwick, Coventry, UK
- H. H. Wills Physics Laboratory, Royal Fort, Bristol, UK
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Sánchez-Monroy X, Torres-Arenas J, Gil-Villegas A. Theoretical equations of state for a charged fluid. J Chem Phys 2019; 150:144507. [PMID: 30981249 DOI: 10.1063/1.5063577] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this article, we present a molecular thermodynamic study of a system of N particles contained within a volume V and interacting via a hard-core pair potential with an attractive interaction according to the Wolf model for charged systems. This variable-range potential is characterized by three parameters: the repulsive hard-core diameter σ, the energy-well depth ϵ, and the inverse range α; a fourth parameter of the model is a cut-off distance xc that depends on α according to the relation xc = 2/α. Two equations of state (EOSs) are presented and derived from thermodynamic perturbation theory and Monte Carlo (MC) simulation data. The first EOS is given by the standard Zwanzig's high-temperature expansion of the Helmholtz free energy, where the first three perturbation terms a1, a2, and a3 were obtained from MC simulations in the canonical ensemble (NVT) and parameterized as functions of α and the reduced density of particles ρ* = Nσ3/V. The second EOS was obtained from the discrete perturbation theory applied to a discrete representation of the Wolf potential. Results for pressures, internal energies, and isochoric heat capacities are compared to the MC computer simulation data of the Wolf system, including vapor-liquid coexistence curves, for different values of α. Overall, both EOSs give a very good representation of the thermodynamic properties of the Wolf fluid when 0.3 ≤ α ≤ 1.0 and 0.05 ≤ ρ* ≤ 0.8. Since the Yukawa fluid can reproduce information of screened ionic interactions, we discuss the equivalence between the Wolf and Yukawa fluids in the context of equivalent systems in liquid theory.
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Affiliation(s)
- X Sánchez-Monroy
- División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León Guanajuato, Mexico
| | - J Torres-Arenas
- División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León Guanajuato, Mexico
| | - A Gil-Villegas
- División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León Guanajuato, Mexico
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6
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Hernández-Martínez LF, Chávez-Navarro MA, González-Tovar E, Chávez-Páez M. A Monte Carlo study of the electrical double layer of a shape-asymmetric electrolyte around a spherical colloid. J Chem Phys 2018; 149:164905. [PMID: 30384730 DOI: 10.1063/1.5038797] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper, we present a Monte Carlo simulation study on the structure of the electrical double layer around a spherical colloid surrounded by a binary electrolyte composed of spherical and non-spherical ions. Results are provided for the radial distribution functions between the colloid and ions, the orientation correlations between the colloid and non-spherical particles, and the integrated charge. Work is reported mainly for non-spherical particles modeled as spherocylinders, although a particular comparison is made between spherocylindrical particles and dimers. For the conditions investigated here, spherocylinders and dimers produce essentially the same structural information. Additionally, it is shown that spherocylinders mostly orient tangentially to the colloid at its surface; this preferred orientation disappears for larger distances. We also evidence that, near the colloid, the integrated charge attenuates monotonically when the macroparticle is highly charged, whereas for intermediate and low charged states of the colloid, the integrated charge can display charge reversal, overcharging, or both, with magnitudes that are sensitive to the salt concentration and to the localization of charge inside the spherocylinders.
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Affiliation(s)
| | - Moisés Alfonso Chávez-Navarro
- Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, S.L.P., Mexico
| | - Enrique González-Tovar
- Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, S.L.P., Mexico
| | - Martín Chávez-Páez
- Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, S.L.P., Mexico
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7
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Packing densification of binary cylindrical particle mixtures under 3D mechanical vibrations. ADV POWDER TECHNOL 2016. [DOI: 10.1016/j.apt.2016.09.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Wu L, Malijevský A, Jackson G, Müller EA, Avendaño C. Orientational ordering and phase behaviour of binary mixtures of hard spheres and hard spherocylinders. J Chem Phys 2015; 143:044906. [DOI: 10.1063/1.4923291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Affiliation(s)
- Liang Wu
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Alexandr Malijevský
- Department of Physical Chemistry, ICT Prague, 166 28 Praha 6, Czech Republic, and Institute of Chemical Process Fundamentals of ASCR, 16502 Praha 6, Czech Republic
| | - George Jackson
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Erich A. Müller
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Carlos Avendaño
- School of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, Manchester M13 9PL, United Kingdom
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Wensink HH, Trizac E. Generalized Onsager theory for strongly anisometric patchy colloids. J Chem Phys 2014; 140:024901. [PMID: 24437905 DOI: 10.1063/1.4851217] [Citation(s) in RCA: 13] [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 implications of soft "patchy" interactions on the orientational disorder-order transition of strongly elongated colloidal rods and flat disks is studied within a simple Onsager-van der Waals density functional theory. The theory provides a generic framework for studying the liquid crystal phase behaviour of highly anisometric cylindrical colloids which carry a distinct geometrical pattern of repulsive or attractive soft interactions localized on the particle surface. In this paper, we apply our theory to the case of charged rods and disks for which the local electrostatic interactions can be described by a screened-Coulomb potential. We consider infinitely thin rod like cylinders with a uniform line charge and infinitely thin discotic cylinders with several distinctly different surface charge patterns. Irrespective of the backbone shape the isotropic-nematic phase diagrams of charged colloids feature a generic destabilization of nematic order at low ionic strength, a dramatic narrowing of the biphasic density region, and a reentrant phenomenon upon reducing the electrostatic screening. The low screening regime is characterized by a complete suppression of nematic order in favor of positionally ordered liquid crystal phases.
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Affiliation(s)
- H H Wensink
- Laboratoire de Physique des Solides - UMR 8502, Université Paris-Sud and CNRS, 91405 Orsay Cedex, France
| | - E Trizac
- Laboratoire de Physique Théorique et Modèles Statistiques - UMR 8626, Université Paris-Sud and CNRS, 91405 Orsay Cedex, France
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Viveros-Méndez PX, Gil-Villegas A, Aranda-Espinoza S. Monte Carlo computer simulation of sedimentation of charged hard spherocylinders. J Chem Phys 2014; 141:044905. [PMID: 25084954 DOI: 10.1063/1.4890819] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e(2)/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions Lx ≈ Ly and Lz = 5Lx, where Lx, Ly, and Lz are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface.
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Affiliation(s)
- P X Viveros-Méndez
- Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo, La Bufa s/n, 98060 Zacatecas, Zacatecas, México
| | - Alejandro Gil-Villegas
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, México
| | - S Aranda-Espinoza
- Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo, La Bufa s/n, 98060 Zacatecas, Zacatecas, México
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12
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Wu C, Chan DY, Tabor RF. A simple and accurate method for calculation of the structure factor of interacting charged spheres. J Colloid Interface Sci 2014; 426:80-2. [DOI: 10.1016/j.jcis.2014.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Revised: 03/08/2014] [Accepted: 03/10/2014] [Indexed: 10/25/2022]
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13
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Jiménez-Serratos G, Gil-Villegas A, Vega C, Blas FJ. Monte Carlo simulation of flexible trimers: From square well chains to amphiphilic primitive models. J Chem Phys 2013; 139:114901. [PMID: 24070305 DOI: 10.1063/1.4820530] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Guadalupe Jiménez-Serratos
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías Campus León, Universidad de Guanajuato, Colonia Lomas del Campestre, León 37150, Mexico
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14
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Green MJ. Isotropic-nematic phase separation and demixing in mixtures of spherical nanoparticles with length-polydisperse nanorods. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/polb.23126] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Morales-Anda L, Wensink HH, Galindo A, Gil-Villegas A. Anomalous columnar order of charged colloidal platelets. J Chem Phys 2012; 136:034901. [PMID: 22280777 DOI: 10.1063/1.3673877] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Monte Carlo computer simulations are carried out for a model system of like-charged colloidal platelets in the isothermal-isobaric ensemble (NpT). The aim is to elucidate the role of electrostatic interactions on the structure of synthetic clay systems at high particle densities. Short-range repulsions between particles are described by a suitable hard-core model representing a discotic particle. This potential is supplemented with an electrostatic potential based on a Yukawa model for the screened Coulombic potential between infinitely thin disklike macro-ions. The particle aspect-ratio and electrostatic parameters were chosen to mimic an aqueous dispersion of thin, like-charged, rigid colloidal platelets at finite salt concentration. An examination of the fluid phase diagram reveals a marked shift in the isotropic-nematic transition compared to the hard cut-sphere reference system. Several statistical functions, such as the pair correlation function for the center-of-mass coordinates and structure factor, are obtained to characterize the structural organization of the platelets phases. At low salinity and high osmotic pressure we observe anomalous hexagonal columnar structures characterized by interpenetrating columns with a typical intercolumnar distance corresponding to about half of that of a regular columnar phase. Increasing the ionic strength leads to the formation of glassy, disordered structures consisting of compact clusters of platelets stacked into finite-sized columns. These so-called "nematic columnar" structures have been recently observed in systems of charge-stabilized gibbsite platelets. Our findings are corroborated by an analysis of the static structure factor from a simple density functional theory.
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Affiliation(s)
- L Morales-Anda
- Departamento de Ingeniería Física, División de Ciencias e Ingenierías Campus León, Universidad de Guanajuato, Colonia Lomas del Campestre, León 37150, México
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16
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Viveros-Méndez PX, Gil-Villegas A. Computer simulation of sedimentation of ionic systems using the Wolf method. J Chem Phys 2012; 136:154507. [DOI: 10.1063/1.4704743] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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17
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Jiménez-Serratos G, Avendaño C, Gil-Villegas A, González-Tovar E. Computer simulation of charged hard spherocylinders at low temperatures. Mol Phys 2011. [DOI: 10.1080/00268976.2010.524171] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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18
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Jha PK, Sknepnek R, Guerrero-García GI, Olvera de la Cruz M. A Graphics Processing Unit Implementation of Coulomb Interaction in Molecular Dynamics. J Chem Theory Comput 2010; 6:3058-65. [DOI: 10.1021/ct100365c] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Prateek K. Jha
- Department of Chemical and Biological Engineering, Department of Materials Science and Engineering, and Department of Chemistry, Northwestern University, Evanston Illinois 60201
| | - Rastko Sknepnek
- Department of Chemical and Biological Engineering, Department of Materials Science and Engineering, and Department of Chemistry, Northwestern University, Evanston Illinois 60201
| | - Guillermo Iván Guerrero-García
- Department of Chemical and Biological Engineering, Department of Materials Science and Engineering, and Department of Chemistry, Northwestern University, Evanston Illinois 60201
| | - Monica Olvera de la Cruz
- Department of Chemical and Biological Engineering, Department of Materials Science and Engineering, and Department of Chemistry, Northwestern University, Evanston Illinois 60201
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