Grand canonical Monte Carlo using solvent repacking: Application to phase behavior of hard disk mixtures

A new "solvent repacking Monte Carlo" strategy for performing grand canonical ensemble simulations in condensed phases is introduced and applied to the study of hard-disk systems. The strategy is based on the configuration-bias approach, but uses an auxiliary biasing potential to improve t...

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Bibliographic Details
Published in:The Journal of chemical physics 2015-09, Vol.143 (12), p.124109-124109
Main Author: Kindt, James T
Format: Article
Language:English
Subjects:
APPROXIMATIONS
BINARY MIXTURES
Chemical potential
Computer simulation
Correlation analysis
CORRELATIONS
Dependence
Dilution
Disk drives
Disks
Domains
EFFICIENCY
Hard disks
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
MAGNETIC DISKS
MONTE CARLO METHOD
Nanoemulsions
Organic chemistry
Packaging
PARTICLES
Phases
SIMULATION
SOLUTES
SOLVENTS
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Summary:A new "solvent repacking Monte Carlo" strategy for performing grand canonical ensemble simulations in condensed phases is introduced and applied to the study of hard-disk systems. The strategy is based on the configuration-bias approach, but uses an auxiliary biasing potential to improve the efficiency of packing multiple solvent particles in the cavity formed by removing one large solute. The method has been applied to study the coexistence of ordered and isotropic phases in three binary mixtures of hard disks with a small mole fraction (xL < 0.02) of the larger "solute" component. A chemical potential of 12.81 ± 0.01 kBT was found to correspond to the freezing transition of the pure hard disk "solvent." Simulations permitted the study of partitioning of large disks between ordered and isotropic phases, which showed a distinct non-monotonic dependence on size; the isotropic phase was enriched approximately 10-fold, 20-fold, and 5-fold over the coexisting ordered phases at diameter ratios d = 1.4, 2.5, and 3, respectively. Mixing of large and small disks within both phases near coexistence was strongly non-ideal in spite of the dilution. Structures of systems near coexistence were analyzed to determine correlations between large disks' positions within each phase, the orientational correlation length of small disks within the fluid phases, and the nature of translational order in the ordered phase. The analyses indicate that the ordered phase coexists with an isotropic phase resembling a nanoemulsion of ordered domains of small disks, with large disks enriched at the disordered domain interfaces.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4931731