[Pw_forum] Cr GGA potential is underestimating the cohesive energy.

[Paolo Giannozzi]

On Oct 17, 2009, at 11:31 , udayagiri sai babu wrote:

> I am calculated the cohesive energy of Cr using the pseudopotential  
> Cr.pbe-sp-van.UPF. I got is 3.63 ev/atom as the cohesive energy  
> where as the experimental value is 4.1 ev/atom. As i know the GGA  
> pseudopotential should overestimate the cohesive energy value

should it? LDA overestimates, GGA not necessarily so.

The cohesive energy of Cr has been already calculated by many authors,
for sure. You may want to have a look at what other people have done
before you. For instance, here:
http://dare.ubvu.vu.nl/bitstream/1871/9949/1/B4.pdf
(found in 5' of google search). They get 3.58eV for Becke-Perdew,
3.80eV for Perdew-Wang. So 3.63eV for PBE after all is not that bad.

P.
---
Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222