DFTB+ & phonopy calculation

How to run

DFTB+ phonon band structures are created as follows:

  1. Create a DFTB+ input file dftb_in.hsd that is set up to perform a single-point energy and force calculation for a structure which is named geo.gen. The dftb_in.hsd file should turn on force evaluation by setting CalculateForces = Yes in its analysis block, and write the tagged results by enabling WriteResultsTag = Yes in its options.

  2. Generate the the required set of structures and the disp.yaml file by issuing the command

    % phonopy -d --dim="4 4 4" --dftb+
    

    This example builds 2 x 2 x 2 supercell files. The undistorted supercell is stored in geo.genS, while the required displacements are stored in files matching the pattern geo.genS-*. Note that you have to increase the supercell dimension until you reach convergence of the band structure.

  1. For each each geo.genS-* structure perform a DFTB+ calculations, retaining the resulting detailed.out file.

  2. Create the FORCE_SETS file with the command

    % phonopy -f disp-*/results.tag --dftb+  ...
    

    Where the location of all of the results.tag files is given on the command line. To run this command, the disp.yaml file has to be located in the current directory, because the atomic displacements are written into the FORCE_SETS file.

  3. Create a band.conf file to specify the path in the Brillouin zone you are interested in (see the phonopy documentation). Then post-process the phonopy data, either in the settings file (DIM) or by providing the dimensions of the the supercell repeat on the command line

    % phonopy -p band.conf --dim="4 4 4" --dftb+
    
  4. Create a band structure in gnuplot format

    % phonopy-bandplot --gnuplot band.yaml > band.dat
    

All major phonopy options should be available for the DFTB+ interface.