PHONON_GAMMA_DIRECTIONS (.cell)

Keyword type

Block

Description

This data block contains a list of directions of approach to gamma point. These are used to evaluate the non-analytical part of the LO/TO phonon splitting. It has the following format:

%BLOCK PHONON_GAMMA_DIRECTIONS
	R1i     R1j     R1k 
	R2i     R2j     R2k 
	.
	.
	.
%ENDBLOCK PHONON_GAMMA_DIRECTIONS

The three numbers on each line are the fractional positions of the k-point relative to the reciprocal space lattice vectors. The k-points define a continuous sequence of straight line segments. The path will be open unless the first and last point in the list are identical.

This block affects the calculated phonon frequencies only if the PHONON_CALC_LO_TO_SPLITTING keyword in the .param file is set to TRUE.

Example

%BLOCK PHONON_GAMMA_DIRECTIONS
	1.0 0.0 0.0
	0.0 0.0 1.0
%ENDBLOCK PHONON_GAMMA_DIRECTIONS
See Also:

CASTEP keyword glossary
CASTEP cell keywords and data blocks

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