[Pw_forum] hyperfine calculation

[Davide Ceresoli]

Jones Tsz-Kai Wan wrote:
> Dear pwscf users
> 
> Does anyone here have experience on HF calculation using gipaw?
> 
> I made extensive test on hyperfine tensor calculation using the gipaw
> code, and I couldn't get reasonable result except free hydrogen atom.
> For H atom, the Fermi contact term (A_s) obtained (~1480) is within
> 10% of published work [e.g. Van de Walle and Blochl, PRB 47, 4244
> (1993)]. However, the results for Si is unreasonable. The Fermi
> contact is only ~ 1% of the published data, and the dipole term (A_p)
> is zero, which is impossible.
> 
> Jones Wan
> 
> Published result:
> A_s ~ 1400 for H, A_s ~ -4200 and A_p ~ -100 [Van de Walle, PRB 47,
> 4244 (1993)].
Dear Jones Wan,
     because in Si the spin-density comes from p orbitals. The exchange
potential generated by the p orbitals, polarizes slightly the 3s orbital,
strongly the 2s electrons, which are not included in the pseudopotential.
One has to perform the core-relaxation. For further details, see the
following post:
http://www.democritos.it/pipermail/pw_forum/2009-September/014475.html

Davide