FERWE and FERDO syntax

Message

anurag · #1 Post by **anurag** » Sun Jan 25, 2009 12:23 am

Hello Everyone,

I would like to manually specify the occupancy level for each band for a system. I am not quite sure how to specify the FERWE and FERDO though I saw some questions on these input tags in the forum.

I have a system with about 204 bands (filled + unoccupied), 8 k points (weight=0.125 for each) and 194 (and 193) electrons in spin up (and spin down).

I would like to do a calculation with the electron in band 194 (spin up) "emptied" and promoted to band 201.

how to specify FERDO and FERWE in such a scenario ? is the following syntax correct ?

FERWE= 0.125(band1,1) 0.125(band2,1) ...0.125(band193,1) 0.125(band194,0) .. 0.125(band200,0) 0.125(band201,1) 0.125(band202,0) ..

FERDO=0.125(band1,1) 0.125(band2,1) ...0.125(band193,1) 0.125(band194,0) .. 0.125(band200,0) 0.125(band201,0) 0.125(band202,0) ..

where 0.125 is the weight for each k-point and I have repeat this string for every k-point.

I read a reply from admin that I have to recompile vasp.4.lib and vasp.4.6 with
define LONGCHAR
set in drdatab.F (vasp.4.lib) (thanks for this information)

best regards,
Anurag

#2 Post by **admin** » Wed Jan 28, 2009 4:41 pm

Please note that the weights of the k-poins are calculated separately and are explicitely multiplied to the weight of a state (in the BZ). Therefore they do not have to be included in FERWE and FERDO.
FERWE and FERDO just correspond to the occupancy in electrons, regardless of the weight with which this particular k-point contributes to the BZ integration.
btw:
instead of giving 1.0 1.0 1.0 1.0 ... you can also give 4*1.0 in INCAR, which makes your input line considerably shorter
[ Edited Wed Jan 28 2009, 06:02PM ]