FourPhonon: An extension module to ShengBTE for computing four-phonon scattering rates and thermal conductivity

Abstract FourPhonon is a computational package that can calculate four-phonon scattering rates in crystals. It is built within ShengBTE framework, which is a well-recognized lattice thermal conductivity solver based on Boltzmann transport equation. An adaptive energy broadening scheme is implemented for the calculation of four-phonon scattering rates. In analogy with thirdorder.py in ShengBTE , we also provide a separate python script, Fourthorder.py , to calculate fourth-order interatomic force constants. The extension module preserves all the nice features of the well-recognized lattice thermal conductivity solver ShengBTE , including good parallelism and straightforward workflow. In this paper, we discuss the general theory, program design, and example calculations on Si, BAs and LiCo O 2 . Program summary Program Title: FourPhonon CPC Library link to program files: https://doi.org/10.17632/jjcwt5436h.1 Developer's repository link: https://github.com/FourPhonon Licensing provisions: GNU General Public License version 3 Programming language: Fortran 90, MPI Nature of problem: Calculation of lattice thermal conductivity and related quantities, determination of both three-phonon and four-phonon scattering rates Solution method: Four-phonon scattering rates at RTA level, adaptive broadening scheme Additional comments including restrictions and unusual features: For a productive run, one needs to use High Performance Computing facilities and it takes several hours to several days to finish calculations