Lattice thermal conductivity with 4th order force constants

[R3aptor]

TDEP is able to extract the force constants up to the 4th order from molecular dynamics trajectory. Is it possible to include 4th order force constants into lattice thermal conductivity calculation implemented in TDEP? Or some external software is required?

[flokno]

@OrbitalC enjoy

[OrbitalC]

Hello @R3aptor
We had a recent update (more a makeover actually) of the binary thermal_conductivity that supports four-phonon contribution to the thermal conductivity (you might have to update your TDEP installation if you installed it more than 3 months ago)
In it, the fourth-order contribution is enabled with the --fourthorder flag, which needs a infile.forceconstant_fourthorder file.
With this binary, you can also use a Monte-Carlo integration scheme to speed-up calculations with the --qg4ph X Y Z flag (where X, Y and Z are grid density for the integration) - it also works for three-phonon contribution with --qg3ph X Y Z. You can find details for the implementation of this binary in this preprint.