Quantum Self-Consistent Ab-Initio Lattice Dynamics

TL;DR

QSCAILD is a Python library for calculating temperature-dependent lattice dynamics in crystals, incorporating anharmonic effects using quantum statistics, and interfacing with external force calculators like DFT.

Contribution

It introduces a new computational tool that combines quantum statistical methods with ab-initio force calculations for lattice dynamics analysis.

Findings

Successfully applied to SrTiO3 cubic perovskite

Computes effective interatomic force constants at finite temperatures

Includes anharmonic effects in lattice dynamics

Abstract

The Quantum Self-Consistent Ab-Initio Lattice Dynamics package (QSCAILD) is a python library that computes temperature-dependent effective 2nd and 3rd order interatomic force constants in crystals, including anharmonic effects. QSCAILD's approach is based on the quantum statistics of a harmonic model. The program requires the forces acting on displaced atoms of a solid as an input, which can be obtained from an external code based on density functional theory, or any other calculator. This article describes QSCAILD's implementation, clarifies its connections to other methods, and illustrates its use in the case of the SrTiO3 cubic perovskite structure.