I have calculated spin-density using CASSCF with the following line
$eldens spind=.t. ieden=1 where=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.