[gpaw-users] PW91 functional

[Lara Ferrighi]

>
> I do not care about total energies, but I remember that there where huge
> differences between PBE, PW91, TPSS and M06L, when I calculated the  
> energies
> using PBE orbitals. E.g. TPSS is often positive, where the others are
> negative, but this depends on the elements in the molecules I've  
> calculated.
> The relative energies where always reasonable, however.
>
I agree with you. I've actually made tests on Au2 not long ago doing  
non-self consistent
MGGA on top of either PBE or LDA and I got:

On top of PBE:
pbe -2.65650
dem06  -12.3524367408 detpss  21.7540271021 derevtpss  116.154094793
Dissociations Au2/Au (exp:-2.30)
M06L : -2.34
TPSS : -2.26
revTPSS: -2.36


On top of LDA:
lda -3.16791
dem06  -573.227942033 detpss  -539.854133548 derevtpss  -445.616037556
Dissociations Au2/Au (exp:-2.30)
M06L : -2.34
TPSS : -2.27
revTPSS: -2.37

So the absolute energies are very different but relative energies are  
always correct.

I'm not sure if it is of any help.

Lara