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Re^2: Spin density from CASSCF in a cube file

Pavlo Solntsev

Dear Alex.

If i understood correctly, rhoalpha-rhobeta is an approximation in case of MCSCF wave function. Or this equation corresponds to determinant(CSF) part, where the two sets of orbitals available in a clear form. Is it safe to ignore negative sign for the analysis of spin-density? In my case, i have a doublet. And a picture i got, actually, perfect.


On Wed Jul 23 '14 1:15pm, Alex Granovsky wrote
>Dear Pavlo,

>With Firefly, the computed spin density is always rhoalpha-rhobeta density.
>It is identically zero for singlets, but is a nontrivial function
>for other multiplicities. For instance, it does not necessary have
>the constant sign despite an excess of alpha electrons. The chemical
>meaning of this is in the beta electron density becomes polarized by
>the alpha electrons so that there are areas with excess of beta spins.

>Hope this helps.

>All the best,
>On Tue Jul 22 '14 6:01pm, Pavlo Solntsev wrote
>>Dear Alex and all forum users.

>>I have calculated spin-density using CASSCF with the following line
>> $eldens spind=.t. ieden=1 where=cube  $end
>> $cube $end
>>I got my cube file, it looks good to me. But i realized it contains surface of two different signs: negative and positive. The positive sign in a spin density surface corresponding to a localization of electron(s). It makes total sense from the picture i got. But negative sign is not clear to me. Does it represent a hole? Does it have a chemical meaning? Do we need to worry about negative sign if we are interesting in location of the electron?

>>I know, that spin density within UHF wavefunction is alpha-beta surface. But what about MCSCF wave function?

>>Maybe someone from this forum has a reference related to the idea about spin density. It would be great.


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