Using bond-length dependent transferable force constants to predict vibrational entropies in Au-Cu, Au-Pd, and Cu-Pd alloys

TL;DR

This paper introduces a length-dependent transferable force constant model to efficiently predict vibrational entropies in various Au-Cu, Au-Pd, and Cu-Pd alloys, including disordered and ordered phases, based on first-principles calculations.

Contribution

The study develops and validates a novel length-dependent force constant model for rapid vibrational entropy prediction in alloy phases, improving computational efficiency.

Findings

Accurate prediction of vibrational entropies for multiple alloy phases.

Transferable force constants depend on bond length and fit to first-principles data.

Vibrational entropy differences between ordered and disordered phases are quantified.

Abstract

A model is tested to rapidly evaluate the vibrational properties of alloys with site disorder. It is shown that length-dependent transferable force constants exist, and can be used to accurately predict the vibrational entropy of substitutionally ordered and disordered structures in Au-Cu, Au-Pd, and Cu-Pd. For each relevant force constant, a length- dependent function is determined and fitted to force constants obtained from first-principles pseudopotential calculations. We show that these transferable force constants can accurately predict vibrational entropies of L1$_{2}$-ordered and disordered phases in Cu$_{3}$Au, Au$_{3}$Pd, Pd$_{3}$Au, Cu$_{3}$Pd, and Pd$_{3}$Au. In addition, we calculate the vibrational entropy difference between L1$_{2}$-ordered and disordered phases of Au$_{3}$Cu and Cu$_{3}$Pt.