# First-Principles Lattice Dynamics Method for Strongly Anharmonic Crystals

## TL;DR

This paper introduces a nonperturbative first-principles lattice dynamics method based on self-consistent phonon theory, enabling accurate analysis of strongly anharmonic crystals where traditional methods fail.

## Contribution

The paper presents a novel computational approach that efficiently incorporates anharmonic effects nonperturbatively using recent numerical techniques and self-consistent phonon theory.

## Key findings

- Accurately predicts phonon frequencies in cubic strontium titanate
- Successfully calculates lattice thermal conductivity in strongly anharmonic materials
- Demonstrates compatibility with hybrid exchange-correlation functionals

## Abstract

We review our recent development of a first-principles lattice dynamics method that can treat anharmonic effects nonperturbatively. The method is based on the self-consistent phonon theory and temperature-dependent phonon frequencies can be calculated efficiently by incorporating recent numerical techniques to estimate anharmonic force constants. The validity of our approach is demonstrated through applications to cubic strontium titanate, where overall good agreements with experimental data are obtained for phonon frequencies and lattice thermal conductivity. We also show the feasibility of highly accurate calculations based on a hybrid exchange-correlation functional within the present framework. Our method provides a new way for studying lattice dynamics in severely anharmonic materials where the standard harmonic approximation and the perturbative approach break down.