MAGMOM (.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 as:

(N^up-N^down)/(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 (4-2)/6 = 0.3333. If the MAGMOM keyword is found in the list of atoms at least once, CASTEP assumes zero spin polarization for all atoms without the qualifier.

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

The MAGMOM keyword is deprecated; an easier to use substitute is the SPIN keyword.

Example

%BLOCK POSITIONS_FRAC
    Fe 0.00    0.00    0.00
    Fe 0.50    0.50    0.00 MAGMOM= 0.5
    Fe 0.50    0.00    0.50 MAGMOM : -0.2
    Fe 0.00    0.50    0.50 MAGMOM 0.5
%ENDBLOCK POSITIONS_FRAC

See Also:

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