[Pw_forum] problem of cutoff convergence
plain110 at gmail.com
Sat Nov 1 00:16:17 CET 2008
I met a problem with cutoff convergence when I ran the Si nanowire self
consistent calculation to get the lda band gap.
I found a big jump 0.3-0.4ev of band gap at 45Ry. Before and after this
point, the band gap curve is flat.
(HOMO does not change much, but lumo had a big jump. )
And the position of this jump will shift with different structure (before
I relaxed the structure, this big jump was at 30Ry.)
I used Si.pz-vbc.UPF, H.pz-vbc.UPF, poseudopotential to run this
I found similar thing when I calculate silane band gap. The jump of 0.4ev
happens at 60-65Ry. And I used the same poseudopotential to calculate.
So what can be the reason for this big jump in band gap with respect to
thank you very much!
university of california, Davis
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