Temperature dependence in interatomic potentials and an improved potential for Ti

TL;DR

This paper introduces a method to incorporate electronic entropy into interatomic potentials using the Sommerfeld approximation, improving the modeling of temperature-dependent properties in materials like titanium.

Contribution

It presents a novel approach to include electronic entropy effects in empirical potentials, enhancing their accuracy at finite temperatures.

Findings

The new potential better predicts thermal properties of titanium.

The method allows fixing melting and phase transition temperatures.

Application to titanium demonstrates improved temperature dependence modeling.

Abstract

The process of deriving an interatomic potentials represents an attempt to integrate out the electronic degrees of freedom from the full quantum description of a condensed matter system. In practice it is the derivatives of the interatomic potentials which are used in molecular dynamics, as a model for the forces on a system. These forces should be the derivative of the free energy of the electronic system, which includes contributions from the entropy of the electronic states. This free energy is weakly temperature dependent, and although this can be safely neglected in many cases there are some systems where the electronic entropy plays a significant role. Here a method is proposed to incorporate electronic entropy in the Sommerfeld approximation into empirical potentials. The method is applied as a correction to an existing potential for titanium. Thermal properties of the new model are calculated, and a simple method for fixing the melting point and solid-solid phase transition temperature for existing models fitted to zero temperature data is presented.