[Pw_forum] Si band gap calculated with different functionals

[Paolo Giannozzi]

On Wednesday 26 November 2003 10:22, Danilo Neuber wrote:

> The Si band gaps obtained with the PBE (E_g = 0.585 eV) and the
> LDA-functional (E_g = 0.505 eV) are in very good agreement with the
> results I got with the PPs Si.pbe-rrkj.UPF (E_g = 0.577 eV) and
> Si.pz-vbc.UPF (E_g = 0.506 eV) from the pwscf website; however, for BLYP I
> got a Si band gap of E_g = 0.855 eV.

is the lattice parameter
- the same for all cases, and equal to the experimental one
- the theoretical one for each case, and they are very similar
- the theoretical one for each case, but they are not very similar
- none of the above ?

> could this be a problem in the implementation of the functional?

it could also be a PP problem. Don't assume that parameters
that are good for the generation of a PP with a given 
exchange-correlation functional are automatically good for all
other exchange-correlation functionals

Paolo

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