Coexistence and Criticality in Size-Asymmetric Hard-Core Electrolytes

Abstract

Liquid-vapor coexistence curves and critical parameters for hard-core 1:1 electrolyte models with diameter ratios l

s 2

s 1

1 to 5.7 have been studied by fine-discretization Monte Carlo methods. Normalizing via the length scale s 6

1 2

s 1 1s 2

, relevant for the low densities in question, both T

c (

k B T c s 6

q 2 ) and r

c (

r c s 3 6 ) decrease rapidly (from

0.05 to 0.03 and 0.08 to 0.04, respectively) as l increases. These trends, which unequivocally contradict current theories, are closely mirrored by results for tightly tethered dipolar dimers (with T

c lower by

0% 11% and r

c greater by 37% 12% )