[Pw_forum] ´ð¸´: [Pw_forum] The band gap problem

[Stefano de Gironcoli]

Forgive my ignorance
is TiO2 known to be a direct gap insulator with valence band top and 
conduction band bottom at Gamma ?
Have you drawn the band structure on the main symmetry lines and compared with
experiment/other calculations ?

stefano

Quoting #TAO JUNGUANG# <TAOJ0003 at ntu.edu.sg>:

> Yes, it is very strange, even it agree very well with the experiment value
> (3.2eV). so I am wonder if there are something wrong. And I have double
> checked my input file, nothing I have got. So I put important part of my
> input/output file in the following, hope there is someone who can help me.
>    
> 
> 
> Input file:
>   &CONTROL
>   calculation='nscf',
>   restart_mode='from_scratch',
>    pseudo_dir='/home/tao/pseudo/',
>   prefix='TiO2',
>    tstress=.true.
>   tprnfor=.true.
> /
> &SYSTEM
>  ibrav=6, a=4.594,c=2.958, nat=6,ntyp=2,
>  ecutwfc=50,ecutrho=300,nbnd=32
> /
> &ELECTRONS
>   conv_thr=1.0d-8,
>   mixing_beta=0.7,
>   mixing_mode='plain',
> /
> 
> ATOMIC_SPECIES
>  Ti  47.867   Ti.vdb.UPF
>  O   15.9994  O.vdb.UPF
> 
> ATOMIC_POSITIONS crystal
> Ti 0.00 0.00 0.00
> Ti 0.5  0.5  0.5
> O  0.3053 0.3053 0.00
> O  0.6947 0.6947 0.00
> O  0.1947 0.8053 0.50
> O  0.8053 0.1947 0.50
> K_POINTS 
> 36
>  .........
> Output file 
> 
>  k = 0.0000 0.0000 0.0000     band energies (ev):
> 
>    -48.0513 -48.0328 -24.6394 -24.6394 -24.5918 -24.5555 -24.4560 -24.4560
>    -10.8949  -9.9359  -9.1136  -9.1136   1.4513   1.7754   2.9432   3.3134
>      3.3134   4.5065   4.5065   4.9294   5.9502   6.2828   6.2828   6.9172
>     10.1728  10.2878  10.7490  10.7491  10.8082  12.5115  12.6253  14.3036
> 
>  10.1728-6.9172=3.2556
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
> 




----------------------------------------------------------------
  SISSA Webmail https://webmail.sissa.it/
  Powered by Horde http://www.horde.org/