[Wien] Questions about forces on nuclei in the presence of spin orbit coupling

[Peter Blaha]

> Take a material, in which only one internal freedom x exists, as an example.
> If I do a series of total energy calculations with difference x and find a
> energy surface with respect to x, then I can obtain a force by taking a
> energy derivative with respect to x. Is the force obtained by this method
> meaningful (even in the presence of spin orbit coupling)?

Yes of course. (But once you have calculated the total energies, you can find the minimum
and you don't "need" the forces).

>  > PS: As mentioned in UG, you can switch off SO for light atoms (eg. oxygens), and then the forces for
>  > those atoms are still ok and meaningful.
> ====================================================
> Does this mean that the spin-orbit term of Pulay correction for the
> investigated atom, eg. oxygen, comes from the oxygen itself only,
> and is irrelevant to those atoms around the oxygen?

Yes.

-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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