Thermodynamics of strongly-coupled Yukawa systems near the one-component-plasma limit. II. Molecular dynamics simulations

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Abstract
Molecular dynamics simulations are employed to study the equilibrium thermodynamics of strongly‐coupled systems of particles interacting through the Yukawa potential. Such systems serve, under the Debye–Hückel approximation, as a model for the physical behavior of plasma or colloidal suspensions of charged particulates. The thermodynamics may be characterized in terms of two dimensionless parameters—the ratio κ of the mean interparticle distance to the Debye length, and an approximate measure Γ of the interparticle potential energy in units of the thermal kinetic energy. Employing an accurate representation of infinite periodic boundary conditions, we focus on the regime of weak Debye screening (κ ≲ 1) and strong coupling (Γ≫1). Excess internal energies measured at many points (κ,Γ) are fitted to simple functional forms for the fluid and solid phases, representing extrapolations of the classical one‐component plasma (OCP) limit, κ=0. Quantitative expressions for the Helmholtz free energy and the ‘‘equation of state’’ of the Yukawa system— giving the pressure p in terms of κ and Γ—are thus derived, and the freezing/melting curve in the (κ,Γ) plane is traced as the intersection of the fluid and solid free‐energy surfaces.