[Pw_forum] bandgap of germanium

[Paolo Giannozzi]

On Saturday 31 July 2004 11:04, Bachir Bouhafs wrote:

> [...] I think that you have calculated your band structure at the
> experimental  lattice parameter [...] which is greater than the LDA 
> value. Which means, that you have applied a negative pressure 
> to your crystal, and consequently the band gap increases.

[ please do not post HTML ]

and this is likely to be the main reason of the discrepancy. Other 
factors, such as the pseudopotential, cutoff, number of k-points, 
may contribute to the difference. For instance: in GaAs, the use 
of a nonrelativistic pseudopotential for Ga increases the band gap
by approx. 0.4 eV.

By the way: the tests and examples are NOT meant to give any
realistic description of any realistic systems. 

Paolo
-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
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