Crystallization of classical multi-component plasmas

TL;DR

This paper introduces a semi-analytic method to calculate the phase transition properties of multi-component plasmas, enabling more efficient exploration of complex mixtures relevant to neutron star crusts.

Contribution

The authors extend existing fitting formulas to multi-component plasmas, providing a new approach to study phase transitions beyond previous simulation-based methods.

Findings

Accurately reproduces composition at half-freezing point within 10% of molecular dynamics results.

Enables exploration of phase diagrams for complex mixtures more efficiently than simulations.

Provides insights into the liquid-solid boundary in accreting neutron stars.

Abstract

We develop a method for calculating the equilibrium properties of the liquid-solid phase transition in a classical, ideal, multi-component plasma. Our method is a semi-analytic calculation that relies on extending the accurate fitting formulae available for the one-, two-, and three-component plasmas to the case of a plasma with an arbitrary number of components. We compare our results to those of Horowitz, Berry, & Brown (Phys. Rev. E, 75, 066101, 2007), who use a molecular dynamics simulation to study the chemical properties of a 17-species mixture relevant to the ocean-crust boundary of an accreting neutron star, at the point where half the mixture has solidified. Given the same initial composition as Horowitz et al., we are able to reproduce to good accuracy both the liquid and solid compositions at the half-freezing point; we find abundances for most species within 10% of the simulation values. Our method allows the phase diagram of complex mixtures to be explored more thoroughly than possible with numerical simulations. We briefly discuss the implications for the nature of the liquid-solid boundary in accreting neutron stars.