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MAGMOM = [real array]
|Default: MAGMOM||= NIONS * 1.0||for ISPIN=2|
|= 3 * NIONS * 1.0||for non-collinear magnetic systems (LNONCOLLINEAR=.TRUE.)|
If one is searching for a spin polarised (ferro- or antiferromagnetic) solution, it is usually safest to start from larger local magnetic moments, because in some cases, the default values might not be sufficiently big. A safe default is usually the experimental magnetic moment multiplied by 1.2 or 1.5. It is important to emphasize that the MAGMOM tag is used only, if the CHGCAR file holds no information on the magnetisation density, and if the initial charge density is not calculated from the wavefunctions supplied in the WAVECAR file. This means that the MAGMOM tag is useful for two kind of calculations
Often such calculations converge more reliably to the desired magnetic configuration than calculations of the first kind. Hence, if you have problems to converge to a desired magnetic solution, try to calculate first the non magnetic groundstate, and continue from the generated WAVECAR and CHGCAR file. For the continuation job, you need to set
in the INCAR file.
Starting from VASP.4.4.4, VASP also determines whether the magnetic moments supplied in the MAGMOM line break the symmetry. If they do, the corresponding symmetry operations are removed and not applied during the symmetrization of charges and forces. This means that antiferromagnetic (AFM) calculations can be performed by specifying anti-parallel magnetic moments for the atoms in the cell: The most simple POSCAR-file for a bcc-cell with AFM spin alignment would be
AFM 2.80000 1.00000 .00000 .00000 .00000 1.00000 .00000 .00000 .00000 1.00000 1 1 Carthesian .00000 .00000 .00000 .50000 .50000 .50000
ISPIN = 2 MAGMOM = 1.0 -1.0
specified in INCAR. In a perfectly AFM ordered cell, the total net magnetisation is zero as a matter of fact, but it is possible to determine the local magnetic moments by using the LORBIT tag (and if LORBIT<10 , the RWIGS-tag in addition).