POSITIONS_FRAC (.cell)

Keyword type

Block

Description

This data block contains the ionic positions in fractional coordinates.

The POSITIONS_FRAC or POSITIONS_ABS data block is interpreted as the reactant coordinate data for a transition state search.

The data block has the following format:

%BLOCK POSITIONS_FRAC
	CCC1/I1 	    R1i     R1j     R1k
	CCC2/I2 	    R2i     R2j     R2k
	.
	.
	.
%ENDBLOCK POSITIONS_FRAC	

The first entry on a line is the symbol or atomic number of the ionic species. The correct symbol will be added automatically for atomic species if the atomic number is specified. A symbol can have a maximum of three characters.

The next three entries are real numbers representing the position of the ion in fractions of the unit cell lattice vectors.

Only one of POSITIONS_FRAC and POSITIONS_ABS may be present in a single cell file.

Example

%BLOCK POSITIONS_FRAC
	.
	.
    O     0.7500000000   -0.2500000000    0.2500000000
    Al    0.6955000000    0.2500000000    0.9186000000
	.
	.
%ENDBLOCK POSITIONS_FRAC

See Also:

POSITIONS_ABS
CASTEP keyword glossary
CASTEP cell keywords and data blocks