Si lattice thermal conductivity

CRYSTAL output file is crystal.o. This is the default file name
for the CRYSTAL interface, so the -c crystal.o parameter is not needed

1) Create displaced supercells (4x4x4 for 2nd order FC, 2x2x2 for 3rd order FC):

   phono3py --crystal --dim="2 2 2" --dim-fc2="4 4 4" -d

   Complete CRYSTAL inputs can be prepared manually
   or with the help of a template
   (TEMPLATE for FC2-supercells, TEMPLATE3 for FC3-supercells)

2) Run the supercell input with CRYSTAL
   Here the supercells have been pre-calculated (outputs.tar.gz).

3) Collect forces:

   phono3py --crystal --cf3 supercell-*o
   phono3py --crystal --cf2 supercell_fc2-*o

   Here the pre-calculated forces are available as FORCES_FC2 and FORCES_FC3

4) Create force constant files fc2.hdf5 and fc3.hdf5:

   phono3py --crystal --dim="2 2 2" --dim-fc2="4 4 4" --fc-symmetry

5) Thermal conductivity calculation:

   phono3py --crystal --fc3 --fc2 --dim="2 2 2" --dim-fc2="4 4 4" --mesh="20 20 20" --br

   --br ->  Relaxation time approximation
   With 20x20x20 mesh, the lattice thermal conductivity at 300 K is 164 W m^-1 K^-1.

   Add --isotope for isotope scattering
   Check the effect of --nac for polar systems
