Dear All Does anyone have optomized the Basis set for such calculations?
I've never calculated Fe, but for ZnO, for example, the standart DZP basis set gives Ecoh ~ 14 eV, whereas a crude optmized version ( done just by increasin the Rc till some convergency in the total energy ) gives 8.08 eV ( exp ~ 7.5 ). Cheers Ney On Mon, Mar 15, 2010 at 11:58 AM, Süle Péter <[email protected]> wrote: > > > Dear Marcos, Alexander, > > To be honest, I tried with bsse correction, and no > serious change have been found. > Even with Spinpolarized T, I get the same crude > cohesive energy of -10. eV/atom for bcc Fe > (Ec_exp ~ 4.6 eV/atom). > > PBE/DZP > > a (Ang) E_KS > > 2.87 -1569.6594 30. -1550.6534 > > Ec = 9.5 eV/atom > > RPBE/DZP > > 2.87 -1570.3247 > 30. -1555.1728 > > Ec = 7.5 eV/atom !!!! (this is the best) > > RPBE/DZP+BSSE > > 2.87 -1672.518952 > 30. -1553.344579 > > Ec = 9.6 > > PW92/LDA > > 2.87 -1557.232591 > 30. -1537.053983 > > Ec = 10.1 > > Therefore RPBE performs the best among various xc > functionals, however, still is far from being acceptable. > For me this poor performance for Fe cohesive energy is due > to the weakness of available xc functionals in SIESTA. > In recent publications authors have reported better results > using GGA/PW91 functionals (Ec=5-6 eV/atom), unfortunatelly > this "classic" functional is not available in SIESTA. > > Regards, Peter Sule > > > > > On Fri, 12 Mar 2010, Alexander Vozny wrote: > > No, BSSE would save maybe 0.5 eV but not 5eV. >> My guess, is that you have to do SpinPolarized calculation for single >> atom. >> >>
