Problem in DOS calculation

Problems running VASP: crashes, internal errors, "wrong" results.

Moderators: Global Moderator, Moderator

Message
Author
priya
Newbie
Posts: 10
Joined: Wed Jun 15, 2005 4:18 am

Problem in DOS calculation

I am trying to calculate the DOS for a system which has 3 atoms equivalent to each other by symmetry. The program identifies the correct symmetry at start, while calculating the angular momentum density of states as well as the integrated charge (written at the end of the OUTCAR if RWIGS is given) the program gives them to be inequivalent. The INCAR and POSCAR that I am using is given below. Should some additional flags be given?
----------------------------------------- POSCAR ----------------------------------------------------
System
3.84000000000000
0.9778911174852863 0.0000000000000000 0.0000000000000000
0.0000000000000000 0.9778911174852865 0.0000000000000000
0.0000000000000000 0.0000000000000000 0.9778911174852865
1 1 3
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.5000000000000000 0.5000000000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.0000000000000000 0.5000000000000000 0.5000000000000000
0.5000000000000000 0.0000000000000000 0.5000000000000000

--------------------------------------- INCAR --------------------------------------------------------
ISMEAR = 0
SIGMA=0.1
PREC=ACC

ISTART=1
EDIFF=0.1E-5

NBANDS=120

EMIN= -20.0
EMAX= 15.0
NPTS=700

RWIGS=0.9 0.9 0.9

AMIX=0.2
Last edited by priya on Fri Jul 22, 2005 9:59 am, edited 1 time in total.

Posts: 2922
Joined: Tue Aug 03, 2004 8:18 am

Problem in DOS calculation

the reason of this behaviour is that the
partial (and ONLY the partial ) magnetizations and
charge densities are not symmetrized before they are written to
OUTCAR. (the total charge density is, of course)
Therefore, the difference in the output stems from the difference
in the k-meshes which are generated:
if ISYM is switched off, the irreducible part of the Brillouin
zone is not determined, hence the k-points are spread all over
the 1st BZ, and the partial densities look symmetric, as they in fact are.
if ISYM is switched on, only the irreducible part of the BZ is filled
with k-points, but for the patrial charges no a-posteriori symmetrisation
is done (as should be and is in fact done for the charge densities).
Therefore, these partial quantities may differ slightly,
even for symmetry-equivalent atoms in a unit cell.
Last edited by admin on Fri Jul 22, 2005 12:53 pm, edited 1 time in total.

scerwin
Newbie
Posts: 10
Joined: Mon Jun 20, 2005 8:39 pm
Contact:

Problem in DOS calculation

I would only add that the projected quantities can be very different (not just slightly). For a simple example, see http://cst-www.nrl.navy.mil/~erwin/vasptips/#pdos.
Last edited by scerwin on Wed Jul 27, 2005 3:34 pm, edited 1 time in total.

lmiao
Newbie
Posts: 10
Joined: Tue Sep 06, 2005 9:59 pm

Problem in DOS calculation

I have LORBIT=1 tag in the INCAR file, therefore I see the site projected DOS for each atom in the DOSCAR file. However I have 10 columns data on each atom. I know the first columm is energy, and if column 2-4 is s p d DOS, what are the rest 6 columns? (I have a spin unpolarized calculation, therefore there should be 4 columns in total, isn't it?)
Last edited by lmiao on Wed Sep 07, 2005 10:37 pm, edited 1 time in total.