SPIN (.cell)

Keyword type

Qualifier

Description

This keyword can be added to any line containing atomic coordinates in either POSITIONS_ABS or POSITIONS_FRAC data blocks, to specify the initial spin polarization on a given atom. The value of atomic spin polarization is determined from the electronic configuration of the atom simply as:

N^up-N^down

where N^up and N^down are the numbers of electrons with spin up and down, respectively.

For example, a Cr atom with 4 up and 2 down electrons would have a polarization of 2. If the SPIN keyword is found in the list of atoms at least once, CASTEP assumes zero spin polarization for all atoms without the qualifier.

The SPIN keyword is a substitute for the deprecated MAGMOM keyword.

The SPIN keyword should be specified only in the .cell file for the main SCF calculation.

Example

%BLOCK POSITIONS_FRAC
    Fe 0.00    0.00    0.00
    Fe 0.50    0.50    0.00 SPIN= 4
    Fe 0.50    0.00    0.50 SPIN : -2
    Fe 0.00    0.50    0.50 SPIN 4
%ENDBLOCK POSITIONS_FRAC

See Also:

MAGMOM
POSITIONS_ABS
POSITIONS_FRAC
CASTEP keyword glossary
CASTEP cell keywords and data blocks