convergence problem with isolated Ti atom

Queries about input and output files, running specific calculations, etc.


Moderators: Global Moderator, Moderator

Post Reply
Message
Author
linpo

convergence problem with isolated Ti atom

#1 Post by linpo » Wed Feb 20, 2008 5:53 pm

The seemingly simple run did not converge in 300 electronic steps. I really did not expect the bad convergence. I was trying to find the total energy of an isolated Ti atom, but VASP refused to converge. The INCAR is

--------------------------------------------
SYSTEM = isolated Ti

ISTART = 0; INIWAV = 1; ICHARG = 2
IALGO = 48

PREC = High
ENCUT = 290.00
EDIFFG = -0.01; EDIFF = 1E-5

ISMEAR = 1; SIGMA = 0.2
IBRION = 2; ISIF = 2; NSW = 20

LWAVE = .False.; LCHARG = .False.
#LREAL = .FALSE.
#LPLANE = .TRUE.
NPAR = 1; NSIM = 4

NBANDS = 12
----------------------------------------------

And I used one k-point, Gamma centered. One Ti atom resides in a 10x11x12 cell. The PAW potential is from vasp resposire.

How to improve the convergence? Because it is an isolated atom, it should be easy to set up the job and test. I am curious to see different results.
<span class='smallblacktext'>[ Edited ]</span>
Last edited by linpo on Wed Feb 20, 2008 5:53 pm, edited 1 time in total.

admin
Administrator
Administrator
Posts: 2921
Joined: Tue Aug 03, 2004 8:18 am
License Nr.: 458

convergence problem with isolated Ti atom

#2 Post by admin » Thu Feb 21, 2008 8:57 am

please read the handbook chapter Examples:Atoms. You will at least have to set ISPIN=2 so that Hund's rule can be obeyed.
Also, it makes no sense to set the ionic relaxation tags (IBRION, EDIFFG,NSW,...) for a single atom in an otherwise empty box
Last edited by admin on Thu Feb 21, 2008 8:57 am, edited 1 time in total.

rpf

convergence problem with isolated Ti atom

#3 Post by rpf » Wed Apr 04, 2012 6:15 pm

Hello I have the same problem. I have tried a lot of different ways but It is impossible to get the correct ground state of Ti (and of Zn).

Though I apply the following recipe given by VASP website (as an example) it gives me a ground state with 3.4 magnetic moment. That is weird...

ISYM = 0 ! no symmetry
ISPIN = 2 ! allow for spin polarisation
VOSKOWN = 1 ! this is important, in particular for GGA
ISMEAR = 0 ! Gaussian smearing, otherwise negative occupancies
SIGMA = 0.1 ! intermid. smearing width
AMIX = 0.2 ! mixing set manually
BMIX = 0.0001
NELM = 20 ! 20 electronic steps
ICHARG = 1

Could you please solve this problem? It seems very simple but there is still no solution.
Last edited by rpf on Wed Apr 04, 2012 6:15 pm, edited 1 time in total.

rpf

convergence problem with isolated Ti atom

#4 Post by rpf » Thu Apr 05, 2012 1:32 pm

any solution ?
Last edited by rpf on Thu Apr 05, 2012 1:32 pm, edited 1 time in total.

Post Reply