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" --sym-fc

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

