Comparison of etotal of Osmium in BCC, FCC, and HCP state

[Leo123]

Dear all,

I am trying to prove that etotal is lowest in Osmium's HCP structure among HCP, BCC, and FCC crystal structures, which it should be knowing that HCP is the natural crystal structure for Osmium. But after some calculations, I found that HCP has the highest etotal -101.10 hatree while BCC and FCC have -101.16 hatree and -101.18 hatree.

I predicted lattice parameter for BCC and FCC based on equations in terms of radius as if osmium exist in BCC and FCC, which I got from HCP natural state.

Any thoughts?

Thank you

Leo

[mverstra]

This post is in the wrong forum (response functions here)

In general you need to give us more info, see the nettiquette page.

Also:
1) you need to make sure everything is converged to the digits you show, wrt kpts and ecut
2) your pseudopotential may not be good enough, try oncvpsp potentials and the several PAW datasets
3) this may be a known dft problem - check the literature
4) it could be a free energy issue, with hcp stabilised by the phonon free energy contribution. Did you add this in as well (it's much more work).