FERWE & FERDO tags

[windiks]

Dear all,

according to VASP manual, the FERDO and FERWE tags can be used to
define (partial) occupancies in the INCAR (or WAVECAR) file are which kept fixed throughout SCF runs. FERWE is for closed shell systems (no spin-polarizatioon) and FERDO is for spin-polarized calculations.
Does anybody have (general) examples of INCAR files where one of these tags have been employed?

Thank you.

René

[admin]

for fixing the occupancies in a calculation with 1 kpoint only (e.g
single atoms), there is an example given in the online handbook
http://cms.mpi.univie.ac.at/vasp/vasp/node210.html
Please mind that the occupancies of NBANDS states have to be set for each, FERWE and FERDO.

if there is more than one k-point, the weights have to be specified for each STATE (band, kpoint).
in the input string, the inner loop is over the bands, the outer loop is over the k-points


[ Edited Wed Aug 17 2005, 02:49PM ]

[matusalem]

for non spin polarization

if

nelect=8
nbands=8
nkpts=1

say we want to occupy the first 3 bands, leaving the following 2 half occupied and the remaining empty

FERWE = 3*1 2*0.5 3*0


for spin polarization

FERWE = 5*1 3*0 (spin up)
FERDO = 3*1 5*0 (spin down)

In the case where there is more than one irreducible kpoint

for instance NKPTS = 3

no spin
FERWE = 3*1 2*0.5 3*0 3*1 2*0.5 3*0 3*1 2*0.5 3*0 i.e. repeats the definition of occupation you want for each k-point

spin

FERWE = 5*1 3*0 5*1 3*0 5*1 3*0 (spin up)
FERDO = 3*1 5*0 3*1 5*0 3*1 5*0 (spin down)