[Pw_forum] bandgap of germanium

Paolo Giannozzi giannozz at nest.sns.it
Mon Aug 2 18:01:22 CEST 2004

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.

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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 Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
Piazza dei Cavalieri 7      I-56126 Pisa, Italy

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