Filename for the phonon modes file, as generated by the oct-phonopy-eigenmodes
utility shipped with Octopus. This file is in plain text with the following format (version 1.0;
lines starting with # are treated as comments and are ignored, except within the
mass and eigenvector value blocks):
Version: 1.0
Nmodes: # Number of modes in the file
Natoms: # Number of atoms in the supercell
Np: # Number of primitive cells in the supercell, used to generate the modes
Masses: # followed by Natoms atomic masses (in AMU, free format)
…
frequency: # Angular frequency of first mode (in atomic units)
# Normal mode eigenvector (for first atom)
# Normal mode eigenvector (for second atom)
… # repeated for all atoms in the supercell
alpha: # amplitude weight of the mode: g_m^(-1/2), i.e.
1 for region A (2q = G) and finite systems, 1/sqrt(2) for region B.
For finite systems this line is optional and defaults to 1.
frequency: # Frequency of second mode
…
The order of atoms has to be the same as in the input (or geometry) file; the masses
are used to verify consistency between the phonon calculation and this run.
Note: the full Brillouin zone can be split into 3 regions:
region A: (time reversal invariant points): -q = q + G
region B: -q + G falls in region C
region C: -q + G falls in region B
Eigenvectors of regions B and C can be expressed as real and imaginary components of those of region B only.