Communication: Thermodynamics of condensed matter with strong pressure-energy correlations

Abstract

We show that for any liquid or solid with strong correlation between its NVT virial and potential-energy equilibrium fluctuations, the temperature is a product of a function of excess entropy per particle and a function of density, T=f(s)h(ρ). This implies that (1) the systems isomorphs (curves in the phase diagram of invariant structure and dynamics) are described by h(ρ)T=Const., (2) the density-scaling exponent is a function of density only, and (3) a Grüneisen-type equation of state applies for the configurational degrees of freedom. For strongly correlating atomic systems one has h(ρ)= Σ nC nn3 in which the only non-zero terms are those appearing in the pair potential expanded as v(r)= Σ nv nr -n. Molecular dynamics simulations of Lennard-Jones type systems confirm the theory. © 2012 American Institute of Physics.