[Wien] Force calculations: a problem with Bi

[Rocquefelte]

I agree with you when you say "the forces should be consistent with the 
total energy withing given approximation", but to find the origin of 
this "artefact" you should probably  try different approaches.
Did you try to use another functional? It could be interesting, 
particularly if we consider that the problem is probably related to the 
way the 6s lone pair is described (although if the formal charge of Bi 
is 3+).

Regards

Xavier

mazin a écrit :
> SO is of course physically important, but irrelevant for my question: 
> the forces should be consistent with the total energy withing given 
> approximation.
>
> There is a problem with describing SOMETHING here, and it may very 
> well be the 6s electron. Yet it strikes me as unlikely for two reasons:
> (1) Bi is trivalent here, so the 6s is pretty much empty
> (2) I find null sensitivity to RKmax, while the 6s state is very diffuse.
>
> Do you have any particular experience of doing something 
> not-immediately-obvious with Bi?
>
> Thanks
> IM
>
> Rocquefelte wrote
>
> I also looked at systems containing bithmuth atoms some times ago and I
> just remember that Bi should be treated with care:
> - problem of the description of the 6s lone pair electron
> - necessity or not to add spin-orbit to properly describe the effect of
> this heavy element on the band structure.
>
> In your case, would it be possible that the problem you have to solve is
> related to the difficulty to properly describe the 6s(Bi) lone pair
> electrons?
>
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