| Re: problem with cohesive energies ( No.1 )|
- Date: 2008/12/09 06:16
- Name: T.Ozaki
Using OpenMX3.4, I also calculated the cohesive energy of H2 molecule.
The following is my result.
VPS: H_CA.vps, scf.energycutoff=150Ryd, scf.XcType=LSDA-CA
********************* H6.5-s2 ****** H6.5-s3 ******* H6.5-s4 *******
NSP H (hartree)* -0.444608886408 -0.444608927193 -0.444608992979
SP H (hartree)** -0.477765305885 -0.477942135972 -0.477977695817
opt H2 (hartree)* -1.112057034790 -1.125275162130 -1.130369890431
Ecoh (hartree)** +0.156526423020 +0.169390890186 +0.174414498797
Ecoh (eV)******* +4.259240496797 +4.609295512851 +4.745992926765
The bond length of H2 molecule was optimized for each basis set.
Also, "NSP" and "SP" stand for the non spin polarized and spin polarized
calculations, respectively. Ecoh is defined to be 2*(SP H)-(opt H2).
My result looks better. Also, even if we use the shorter cutoff radius for
the basis set, I guess that the BSSE can be reduced by the
| Re: problem with cohesive energies ( No.2 )|
- Date: 2008/12/05 16:48
- Name: Vlad
- Dear Prof. Ozaki,
thank you for your reply.
I could reproduce your results. And I have found the source of previous discrepancies: in the spin polarized calculations for single atoms I put the same initial charges for alpha and beta spin (e.g. 0.5 0.5 for hydrogen atom), thinking that the spin charges will be refined during SCF cycles. It's not the case. So with LSDA-CA and "Scf.SpinPolarization On" I got simply the same energies as for the non spin polarized calculations.
| Re: problem with cohesive energies ( No.3 )|
- Date: 2008/12/11 21:58
- Name: Vasilii Artyukhov
- Dear Vlad,
since you're putting equal initial occupations for both spins, and there's no mechanism to break this symmetry during your calculation (like, e.g., spin-orbit coupling could do), there's simply no reason to expect the result to be different from that from a non-spin-polarized calculation. :)