Functions in Phonon
PHONON, version 4.28

Phonon ver. 4.28 contains all options of Phonon, ver. 4.24.

The performance of Phonon, ver. 4.28, with respect to ver. 4.24,
is greatly improved.
In particular, for
the "HellmannFeynman/DO Report" option the computing CPU time is
shortened by a factor of 10  100, depending on the supercell size and
symmetry.

There are now two versions to calculate the force constants
from HellmannFeynman forces. First, permits to find the force constants
from single (+/) displacements of nonequivalent atoms of the crystal
unit cell. Second, allows to supplement the HellmannFeynman file by
forces generated by simultaneous displacement of many atoms of supercell,
for example those which form a specially interesting phonon mode.

There is about 140 predefined models with realistic force constants,
or HellmannFeynman forces.
See: