Fast Free Energy Calculations for Unstable High-Temperature Phases

TL;DR

The paper introduces a rapid and precise computational method for vibrational properties of unstable high-temperature phases, enabling efficient calculations of phonon dispersion, free energies, and phase transition temperatures.

Contribution

It presents a novel finite-difference based approach optimized for large displacements to accurately compute vibrational properties of mechanically unstable phases.

Findings

Efficient calculation of phonon dispersion relations.

Accurate free energy and phase transition temperature estimates.

Application to high-temperature phases of Ti, Zr, and Hf.

Abstract

We present a fast and accurate method to calculate vibrational properties for mechanically unstable high temperature phases that suffer from imaginary frequencies at zero temperature. The method is based on standard finite-difference calculations with optimized large displacements and is significantly more efficient than other methods. We demonstrate its application for calculation of phonon dispersion relations, free energies, phase transition temperatures, and vacancy formation energies for body-centered cubic high-temperature phases of Ti, Zr, and Hf.