phonopy/example-phono3py/Si

This is the example of silicon calculation. The supercell is 2x2x2 of the conventinal unit cell. The VASP calculation was made for force calculations with 300 eV, 2x2x2 k-point mesh for the supercell, and PBE-sol. Silicon crystal is F-centre, so there is the transformation matrix from the conventinal unit cell to the primitive cell.

To create fc3.hdf5 and fc2.hdf5,

% phono3py --dim="2 2 2" --sym_fc3r --sym_fc2 --tsym -c POSCAR-unitcell

Using 11x11x11 sampling mesh, lattice thermal conductivity is calculated by

% phono3py --dim="2 2 2" --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" -c POSCAR-unitcell --mesh="11 11 11" --fc3 --fc2 --thm --br

kappa-m111111.hdf5 is written as the result. The lattice thermal conductivity is calculated as 108.9 W/m-K at 300 K. This becomes, with 19x19x19 sampling mesh, 123.2 W/m-K.

Accumulated lattice thermal conductivity is calculated using 'kaccum' script.

% kaccum --mesh="11 11 11" --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" POSCAR-unitcell kappa-m111111.hdf5 |tee kaccum.dat

The plot of this result is shown in Si-kaccum.png. It is found that most of the lattice thermal conductivity owes the phonon modes below 6 THz.

fc2.hdf5 can be read by harmonic phonopy to rename it to force_constants.hdf5. The phonon band structure and DOS are watched by

% cp fc2.hdf5 force_constants.hdf5
% phonopy --dim="2 2 2" --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" -c POSCAR-unitcell --mesh="19 19 19" --band="1/2 1/2 0 0 0 0 1/2 1/2 1/2" --hdf5 --readfc --thm -p

Si-band-DOS.png shows this plot. The shape of phonon DOS below 6 THz is similar to the derivative of the accumulated lattice thermal conductivity, i.e., the heat is conductied by the low frequency longitudinal-acoustic-like modes.