BoltzTraP2, a program for interpolating band structures and calculating semi-classical transport coefficients

TL;DR

BoltzTraP2 is a versatile software tool that interpolates band structures and computes semi-classical transport coefficients using minimal input data, applicable to various materials and capable of going beyond common approximations.

Contribution

It introduces BoltzTraP2, a new software package that efficiently calculates transport properties from band structure data, including beyond the constant relaxation time approximation.

Findings

Successfully reproduces the positive Seebeck coefficient of lithium.

Demonstrates application to silicon and simple parabolic bands.

Provides a flexible tool accessible via command-line and Python.

Abstract

BoltzTraP2 is a software package for calculating a smoothed Fourier expression of periodic functions and the Onsager transport coefficients for extended systems using the linearized Boltzmann transport equation. It uses only the band and $k$-dependent quasi-particle energies, as well as the intra-band optical matrix elements and scattering rates, as input. The code can be used via a command-line interface and/or as a Python module. It is tested and illustrated on a simple parabolic band example as well as silicon. The positive Seebeck coefficient of lithium is reproduced in an example of going beyond the constant relaxation time approximation.