DFTB+ & phonopy calculation¶
How to run¶
DFTB+ phonon band structures are created as follows:
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 = Yesin its analysis block, and write the tagged results by enabling
WriteResultsTag = Yesin its options.
Generate the the required set of structures and the
phonopy_disp.yamlfile by issuing the command
% phonopy -d --dim="4 4 4" --dftb+
This example builds 4 x 4 x 4 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.
For each each
geo.genS-*structure perform a DFTB+ calculations, retaining the resulting
FORCE_SETSfile with the command
% phonopy -f disp-*/results.tag --dftb+ ...
Where the location of all of the
results.tagfiles is given on the command line. To run this command, the
phonopy_disp.yamlfile has to be located in the current directory, because the atomic displacements are written into the FORCE_SETS file.
band.conffile 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+
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.