This package contains a fix phonon command that calculates dynamical
matrices from finite temperature MD simulations, which can then be
used to compute phonon dispersion relations, directly from molecular
dynamics simulations.

It also contains commands to compute the dynamical matrix and third
order tensor at pre-optimized positions through finite differences.

See the doc page for the fix phonon command or the dynamical_matrix
or third_order commands for detailed usage instructions.

Use of this package requires building LAMMPS with FFT suppport, as
described in doc/Section_start.html.

There are example scripts for using commands in this package in
examples/USER/phonon.

There is an auxiliary post-processing tool in tools/phonon that will
compute phonon frequencies and dispersion relations from the dynamical
matrices output by the fix phonon command.

There is also an alternative code, dump2phonon, available which enables
one to use the functions of fix-phonon by reading in atom-style dump
files of lammps (which can be converted from the trajectories of any
other MD code):
   https://github.com/lingtikong/dump2phonon

The person who created fix phonon is Ling-Ti Kong (konglt at
sjtu.edu.cn) at Shanghai Jiao Tong University.  Contact him directly
if you have questions.

The person who created the dynamical_matrix command is Charlie Sievers
(charliesievers at cox.net) at UC Davis. Contact him directly if you
have questions about his code.
