This is the example of the wurtzite-type AlN phono3py calculation. The
VASP code was used with 500 eV and LDA as XC functional. The
experimental lattice parameters were used and the internal positions
of atoms were relaxed by calculation. The 3x3x2 and 5x5x3 supercells
were chosen for fc3 and fc2. The 6x6x4, 2x2x2, 1x1x2 k-point sampling
meshes with Gamma-centre in the basal plane and off-Gamma-centre along
c-axis were employed for the unit cell, fc3 supercell, and fc2
supercell, respectively. For the DFPT calculation of Born effective
charges and dielectric constant, the 12x12x8 k-point sampling mesh
with the similar shift was used.  For the better shape of phonon band
structure, fc2 may be calculated separately by phonopy.

After unzipping FORCES_FC3.lzma, to obtain fc3.hdf5 and normal fc2.hdf5,

% phono3py --dim="3 3 2" --sym-fc -c POSCAR-unitcell

Using 13x13x9 sampling mesh, lattice thermal conductivity is calculated by

% phono3py --dim="3 3 2" -c POSCAR-unitcell --mesh="13 13 9" --fc3 --fc2 --br

kappa-m13139.hdf5 is written as the result. The lattice thermal
conductivity is calculated as k_xx=228.2 and k_zz=224.2 W/m-K at 300 K.

With --nac option, non-analytical term correction is applied reading
the Born effective charges and dielectric constant from BORN file:

% phono3py --dim="3 3 2" -c POSCAR-unitcell --mesh="13 13 9" --fc3 --fc2 --br --nac

This changes thermal conductivity at 300 K to k_xx=224.5 and
k_zz=214.9. The shape of phonon band structure is important to
fullfill energy and momentum conservations. FORCE_SETS for fc2
calculated with phonopy can be reused in phono3py. The following
command creates FORCES_FC2 and disp_fc2.yaml from FORCE_SETS:

% phono3py --fs2f2

To recreate fc2.hdf5, --dim_fc2 option is added to the list of options,

% phono3py --dim="3 3 2" --dim_fc2="5 5 3" --sym-fc -c POSCAR-unitcell

With this fc2, the thermal conductivity is calculated by

% phono3py --dim="3 3 2" --dim_fc2="5 5 3" -c POSCAR-unitcell --mesh="13 13 9" --fc3 --fc2 --br --nac

k_xx=229.4 and k_zz=214.7 are obtained. In the case of this example,
we can see that the larger fc2 supercell contributes little, which
means that the 3x3x2 supercell was good enough to obtain a good shape
of phonon band structure.
