Anharmonic vibrational properties in periodic systems: energy, electron-phonon coupling, and stress

TL;DR

This paper presents a unified first-principles approach to study anharmonic vibrational properties in periodic systems, enabling accurate calculations of phonon-related quantities at finite temperatures.

Contribution

It introduces a theoretical framework that incorporates anharmonic effects into vibrational property calculations, including energy, electron-phonon coupling, and stress.

Findings

Temperature dependence of electronic band gap in diamond, lithium hydride, and lithium deuteride.

Calculation of the vibrational contribution to the stress tensor.

Quantitative analysis of thermal expansion coefficients.

Abstract

A unified approach is used to study vibrational properties of periodic systems with first-principles methods and including anharmonic effects. Our approach provides a theoretical basis for the determination of phonon-dependent quantities at finite temperatures. The low-energy portion of the Born-Oppenheimer energy surface is mapped and used to calculate the total vibrational energy including anharmonic effects, electron-phonon coupling, and the vibrational contribution to the stress tensor. We report results for the temperature dependence of the electronic band gap and the linear coefficient of thermal expansion of diamond, lithium hydride, and lithium deuteride.