## Dynamical matrix

Dnamical matrix at a q-point is constructed by supercell force constants and is written as,

 (3.9)

An element of a dynamical matrix is calculated by the sum of force constants multiplied by phase factor which is a vector product of the q-point and a vector between focused atoms. runs through all unitcells contained in a supercell. In output of fropho, a column () of a dynamical matrix corresponds to a displaced atom number and a row () of that corresponds to an atom number where force is affected. If an atom of a force constant is on a rim of the supercell, the force constant is divided by the multiplicty which the atom is shared by the neighboring supercells.

togo 2009-02-12