Gas-liquid critical point of the ultrasoft restricted primitive model from analytic theory

Patsahan Patsahan

doi:10.5488/cmp.18.24601

Abstract

Gas-liquid criticality in the ultrasoft restricted primitive model (URPM) of polyelectrolytes is studied using the collective variables-based theory. For the model, an effective Hamiltonian is derived and explicit expressions for all the coefficients are found in a one-loop approximation. Based on this Hamiltonian, the phase and critical behaviour is analysed. Our results provide evidence that the nature of the gas-liquid criticality in the URPM is the same as in the restricted primitive model that includes a hard core.

Highlights

Gas-liquid criticality in the ultrasoft restricted primitive model (URPM) of polyelectrolytes is studied using the collective variables-based theory
Contrary to the familiar restricted primitive model (RPM) [3], no hard cores are involved in the URPM
The phase diagram of the model was studied in [1, 2, 6] using Monte Carlo (MC) and molecular dynamic simulations

Summary

Introduction

Gas-liquid criticality in the ultrasoft restricted primitive model (URPM) of polyelectrolytes is studied using the collective variables-based theory. More recently [6], the gas-liquid phase transition and the critical behavior of the URPM have been studied using finite size scaling MC simulations in the grand canonical ensemble. The estimates of the critical point parameters (Tc∗ = 0.0134 and ρ∗c = 0.26) differ from those given in [2], i.e., Tc∗ ∼ 0.018, ρ∗c ∼ 0.16 (expressed in the same reduced units as in [6]) which are obtained for smaller system sizes and without finite scaling size analysis.

Results

Conclusion