Reference interaction site model and optimized perturbation theories of colloidal dumbbells with increasing anisotropy

We investigate thermodynamic properties of anisotropic colloidal dumbbells in the frameworks provided by the Reference Interaction Site Model (RISM) theory and an Optimized Perturbation Theory (OPT), this latter based on a fourth-order high-temperature perturbative expansion of the free energy, rece...

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Bibliographic Details
Published in:The Journal of chemical physics 2015-06, Vol.142 (22), p.224904-224904
Main Authors: Munaò, Gianmarco, Gámez, Francisco, Costa, Dino, Caccamo, Carlo, Sciortino, Francesco, Giacometti, Achille
Format: Article
Language:English
Subjects:
ANISOTROPY
BENCHMARKS
COLLOIDS
COMPARATIVE EVALUATIONS
Computational fluid dynamics
Computer simulation
CRITICAL TEMPERATURE
DIAGRAMS
FREE ENERGY
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
Liquid phases
LIQUIDS
Mathematical models
MEAN-FIELD THEORY
Organic chemistry
Perturbation methods
PERTURBATION THEORY
Phase separation
POTENTIALS
Predictions
REDUCTION
Self-assembly
SPHERES
Temperature dependence
Theory
Thermodynamic properties
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Summary:We investigate thermodynamic properties of anisotropic colloidal dumbbells in the frameworks provided by the Reference Interaction Site Model (RISM) theory and an Optimized Perturbation Theory (OPT), this latter based on a fourth-order high-temperature perturbative expansion of the free energy, recently generalized to molecular fluids. Our model is constituted by two identical tangent hard spheres surrounded by square-well attractions with same widths and progressively different depths. Gas-liquid coexistence curves are obtained by predicting pressures, free energies, and chemical potentials. In comparison with previous simulation results, RISM and OPT agree in reproducing the progressive reduction of the gas-liquid phase separation as the anisotropy of the interaction potential becomes more pronounced; in particular, the RISM theory provides reasonable predictions for all coexistence curves, bar the strong anisotropy regime, whereas OPT performs generally less well. Both theories predict a linear dependence of the critical temperature on the interaction strength, reproducing in this way the mean-field behavior observed in simulations; the critical density—that drastically drops as the anisotropy increases—turns to be less accurate. Our results appear as a robust benchmark for further theoretical studies, in support to the simulation approach, of self-assembly in model colloidal systems.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4922163