[Pw_forum] ZnAlO4 Band gap

[Giovanni Cantele]

The pseudo potentials you use correspond to the following atomic valences:
Zn.pbe-van.UPF : 12
Al.pbe-sp-van.UPF : 11
O.pbe-van_ak.UPF : 6

Therefore, the total amount of electrons per unit cell, as printed in the output (that you should carefully read!) is:

12 * N_Zn + 11 * N_Al +  6 * N_O = 12 * 8 + 11 * 16 + 6 * 32 = 464

This corresponds, if my calculation is not wrong, to 464 / 2 = 232 occupied bands.

If you specify, as you do, nbnd= 200 in the input file for the non self-consistent calculation, the gap you calculate is not
between the highest occupied and the lowest unoccupied bands, but between low energy occupied bands.


Giovanni


> On 15 May 2015, at 16:02, Winfred Mulwa <mulwawinfred at gmail.com> wrote:
> 
> Dear all,
> I am calculating the band gap of ZnAlO4 using the attached inputfile. 
> My results show a band gap of 10eV compared to experimental value of 3.8eV.
> Please somebody tell me where i went wrong.
> Regards
> Mulwa Winfred.
> D Phil Student, Computational Material Science Group,
> University of the Free State - QwaQwa,
> South Africa.
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele