[Pw_forum] the issues with density of state vs. energy plot

[Gabriele Sclauzero]

Il giorno 28/lug/2011, alle ore 01.07, Tram Bui ha scritto:

> Dear Everyone,
>       I have done the DOS calculation for a bulk 3C-SiC (zinc-blend). and I found the Fermi energy (Ef) level is =10.6381 (eV).

3C-SiC is a semiconductor, thus speaking of Fermi Energy in this case does not make much sense because there is a bandgap. If for some reason you want to use smearing, then Ef is used and computed in the calculation. Ef should fall somewhere in the gap, not necessarily at the top of the valence band. In practice it could fall either at the top of the valence band or at the bottom of the conduction band, depending on the value of degauss and on the accuracy of the k-point sampling. In either case, you shouldn't attach much importance to it in the case of an insulator (unless it falls in some other place, then your calculation might have some troubles...).

> so I plot the DOS vs. Energy (eV) for my bulk system and also substract the energy to the Ef in order to have Ef=0 at the top of the valence band. But the plot turned out to be different. The top of the valence band is below 0. I have attached some files here. Would please let me know what I might have done wrong in my input? or what could have been wrong in my plot?

Your DOS looks perfectly reasonable to me. You may need to improve the BZ sampling or reduce the smearing used to plot the DOS. Better would be using the tetrahedra method (see used guide).

Regards,


GS

> 
> Best Regards,
>  
> Tram Bui
> 
> M.S. Materials Science & Engineering
> trambui at u.boisestate.edu
> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne







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