Quantum Self-Consistent Ab-Initio 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. Program summaryProgram Title: QSCAILDCPC Library link to program files:https://doi.org/10.17632/y4c922fwtf.1Licensing provisions: GNU General Public License version 3.0Programming language: PythonExternal routines/libraries: MPI, NumPy, SciPy, spglib, phonopy, sklearnNature of problem: Calculation of effective interatomic force constants at finite temperatureSolution method: Regression analysis of forces from density functional theory coupled with a harmonic model of the quantum canonical ensemble, performed in an iterative way to achieve self-consistency of the phonon spectrum