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RWIGS
RWIGS= [real array]
Default |
|
|
RWIGS |
= |
values read from POTCAR |
The Wigner Seitz radius is optional. It must be supplied for each species in
the POSCAR file i.e.
RWIGS = 1.0 1.5
for a system with 2 species (types of atoms).
If the RWIGS values is supplied and LORBIT
10, the spd- and site projected wavefunction character
of each band is evaluted, and the local partial DOS is calculated.
If LORBIT
10, RWIGS is ignored
(see sections 5.16 and 5.15). RWIGS must be
set in calculations with constraining the local magnetic moments (see section
6.69
For mono-atomic system RWIGS can be defined
unambiguously. The sum of the volume of the spheres around each atom should be
the same as the total volume of the cell (assuming that you do not have a
vacuum region within your cell). This is in the spirit of atomic sphere calculations.
VASP writes a line
Volume of Typ 1: 98.5 %
to the OUTCAR file. You should use a RWIGS value which yields a
volume of approximately
.
For binary systems there is no unambiguous way to define RWIGS and
several choices are possible. In all cases, the sum of
the volume of the spheres should be close to the total
volume of the cell (i.e the sum of the values given by VASP should be
around
).
- One possible choice is to set
RWIGS such that the overlap between the spheres is minimized.
- However in most cases, it is simpler to choose the radius of
each sphere such that they are close to the covalent radius
as tabulated in most periodic tables. This
simple criterion can be used in most cases, and it relies
at least on some ``physical intuition''.
Please keep in mind that results are qualitative -- i.e.
there is no unambiguous way to determine the location of an electron.
With the current implementation, it is for instance
hardly possible to determine charge transfer. What
can be derived from the partial DOS is the typical character of a peak in a DOS.
Quantitative results can be obtained only by carefull comparison with
a reference system (e.g. bulk versus surface).
Next: LORBIT
Up: The INCAR File
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N.B. Requests for support are to be addressed to: vasp.materialphysik@univie.ac.at