4-phonon scattering rates

[cumtra]

Dear Nakib,
Thank you so much for your effort on a wonderful software!
I'm tring to calculate the four-phonon thermal conductivity in the latest release version (elphbolt-v1.1). I want to know what files are needed to calculate the four phonons. Is it necessary to follow this?

Thanks!

[nakib]

Thanks for the kind words, cumtra! Regarding including the 4-phonon scattering rates in elphbolt: yes, at the moment you need to first calculate these with the FourPhonon code. The excerpt above gives all the necessary information. But let me know if anything is unclear. Some time soon I will add an example that includes 4-phonon scattering.

Best,
Nakib

[cumtra]

Dear Nakib,
I follow the manual to add the ‘FourPhonon_BTE.w_4ph_T0.300E+03’ and 'ourPhonon_BTE.qpoint_full' files, and add parameters fourph_mesh_ref = 4 and fourph=true to input.xml. But there is still the following problem.

[nakib]

Did you prepend at the top of this file the number of irreducible q-points that you had in your FourPhonon calculation?

[cumtra]

I prepend at the top of this file the number of irreducible q-points under your suggestion，and the problem was solved. But there are new mistakes(Wrong q-mesh in external 4-ph calculation. Exiting). I set the q-mesh as follows: qmesh = 10 10 10; fourph_mesh_ref = 4.

[nakib]

From the following snippet it looks like the total number of q-points that you prepended at the top of your FourPhonon_BTE.qpoints_full file does not match the number of q-points calculated by elphbolt by dividing the transport q-mesh with number fourph_mesh_ref. Can you share the different wave vector meshes you are using?

       if(this_image() == 1 .and. num%fourph) then
          open(1, file="FourPhonon_BTE.qpoints_full", status="old")

          read(1, *) coarse_numq_full
          if(coarse_numq_full /= product(coarse_qmesh)) then
             call exit_with_message('Wrong q-mesh in external 4-ph calculation. Exiting.')
          end if
       end if

       sync all
       call co_broadcast(coarse_numq_full, 1)
       sync all