[Pw_forum] Si band gap calculated with different functionals

[Danilo Neuber]

Dear PWSCF community!

As an exercise in PP generation, I have created Si pseudopotentials with
Paolo Giannozzi's PP programs.

Using the ground state [Ne] 3s2 3p2 for the s- and p-channels and
[Ne] 3s1.25 3p0.75 3d0.25 (taken from the BHS-paper PRB v26, p. 4199) for
the d-channel of the pseudopotential and accepting the suggested values
for the matching radii r_c (without nonlinear core correction), I created
PPs for the functionals LDA, BLYP and PBE. (I adapted the example
shell scripts from the PP and the pwscf program package for PP generation and
band structure calculation.)

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. This value seems too good to be
true, could this be a problem in the implementation of the functional?

Thank you in advance for any comments!

With kind regards,

Danilo R. Neuber

-- 
Dipl.-Ing. Danilo Neuber <neuber at itp.tu-graz.ac.at>

Technische Universität Graz               Telefon: +43 / 316 / 873 - 8188
Institut für Theoretische Physik          Telefax: +43 / 316 / 873 - 8678
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