FERWE & FERDO tags

Question on input files/tags, interpreting output, etc.

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windiks
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FERWE & FERDO tags

#1 Post by windiks » Tue Aug 16, 2005 1:01 pm

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
Last edited by windiks on Tue Aug 16, 2005 1:01 pm, edited 1 time in total.

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FERWE & FERDO tags

#2 Post by admin » Wed Aug 17, 2005 12:45 pm

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 ]
Last edited by admin on Wed Aug 17, 2005 12:45 pm, edited 1 time in total.

matusalem

FERWE & FERDO tags

#3 Post by matusalem » Thu Aug 30, 2012 11:02 pm

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)
Last edited by matusalem on Thu Aug 30, 2012 11:02 pm, edited 1 time in total.

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