[Pw_forum] Different band gap value from the 'relax' and 'nscf'calculation.

[Felipe Valencia Hernandez]

Dear Tao Junguang,

> order to figure out the reason, I run another one setting
> calculation='relax' with the other parameters the same, and I got the
> value of 1.64eV, which sounds quite reasonable for DFT. So I am wonder
> is any chance that the 'nscf' and 'relax' different so much ?  

Sure they  differ! calculation='relax' request an structural relaxation 
(i.e. the internal coordinates are optimized). Do your initial and final 
coordinates differ significantly? In that case, the reason for the 
differences in the electronic  gaps is quite evident.

Best regards,
Felipe
-- 
Felipe Valencia Hernandez
Dipartimento di Fisica G. Galilei
Via Marzolo 8
I-35131 Padova, Italy


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