[Pw_forum] scf calculation of isolated atom

[Gabriele Sclauzero]

Dear Saibabu,

udayagiri sai babu wrote:
> Dear all
> I am performing a scf cacultion of Cr isolated atom. Below is my input 
> file. I got an error saying *"strange occupations:number of electrons 
> from occupations is wrong"*. I undestood like my occupation card is not 
> matching with my "nbnd" value but i could not correct it can somebody 
> give me some suggestion.

I tried your input file with the CVS version of QE and it works fine. It seems that the 
piece of code parsing the OCCUPATIONS input card has been rewritten in version 4.1. Please 
upgrade your code to the newest version and report to the forum if you find any problem. 
Thanks.

> 
> 2) Can i write occupations card for chromium as
> 1      1 1 1 1 1
> 1      0 0 0 0 0
> 4s1  3d5.

Not like this, but the way you wrote them in the input file below is OK. You must specify 
as many rows as nspin and, for each row, as many occupation factors as nbnd.


> 
> 3) usually what should be the nbnd value?

For non-magnetic insulators it can be as low as nelec/2, while in this case you need to 
specify a higher value since your spin population is unbalanced (the code does not allow a 
different number of spin-up bands and spin-down bands).

Cheers

GS

> 
> -- &control
> calculation = 'scf',
> restart_mode='from_scratch',
> outdir='/home/sai/softwares/espresso-4.0.1/workspace/temp',
> prefix='chromium'
> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
> /
> &system
> ibrav=1
> celldm(1)=15,
> nat=1,
> ntyp=1
> ecutwfc=50,
> ecutrho=500,
> occupations='from_input',
> nspin=2
> starting_magnetization(1)=0.2,
> nbnd=13
> nosym=.true.,
> /
> &electrons
> conv_thr=1.D-8,
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta= 0.3
> electron_maxstep=10000
> /
> ATOMIC_SPECIES
> Cr  51.9961  Cr.pw91-sp-van.UPF
> ATOMIC_POSITIONS (crystal)
> Cr  0.00000000  0.00000000      0.00000000
> K_POINTS {automatic}
> 1 1 1 0 0 0
> OCCUPATIONS
> 1  1 1 1  1  1 1 1 1 1  0 0 0
> 1  1 1 1  0  0 0 0 0 0  0 0 0
>                          
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum

-- 


o ------------------------------------------------ o
| Gabriele Sclauzero, PhD Student                  |
| c/o:   SISSA & CNR-INFM Democritos,              |
|        via Beirut 2-4, 34014 Trieste (Italy)     |
| email: sclauzer at sissa.it                         |
| phone: +39 040 3787 511                          |
| skype: gurlonotturno                             |
o ------------------------------------------------ o