**Atsushi Togo**

This code, *fropho*, is made for analyzing phonon system in
solid. The Parlinski-Li-Kawazoe method is implemented. *fropho*
is supposed to be used with the first-principles calculation with
periodic boundary condition. The theory for phonon calculation is
based on the harmonic approximation. The calculation is made of two
steps. Firstly, supercells which are used for input structures for
the first-principles calculation are prepared in view of crystal
symmetry. Each supercell contains an atomic displacement. Secondary,
the calculated forces on atoms in the supercells are summarized. Then
phonon frequencies and eigenmodes are obtained by solving dynamical
matrices. Pre- and post-processing codes are prepared for ease of
handling calculated data.

- Contents
- Introduction
- How to use fropho

- Inside fropho
- Matrix representation of linear equation
- Code
- Coordinate system
- Symmetry operation rule
- Memory consumption and execution time
- Solve smaller force constant matrices
- Procedure
- Parse input file
- Parse POSCAR
- Get symmetry representations of an input structure
- Build supercell
- Get symmetry representations of the supercell
- Search independent atoms and displacements
- Write DISP and SPOSCAR
- Rebuild unit cell from specified primitive axis
- Create map between unit cell atoms and supercell atoms
- Parse FORCES file
- Get site-point symmetry representations
- Calculate force constants
- Expand force constants to dependent atoms
- Make Q-points list
- Prepare non-analytical terms for LO-TO splitting
- Solve dynamical matrices

- Bibliography
- About this document ...

togo 2009-02-12