[Pw_forum] Something strange in the calculation with the spin=2 and multiplicity=1

[Paolo Giannozzi]

On Jan 13, 2010, at 6:41 , vega lew wrote:

> I have compare the results of two calculation for singlet state  
> with or without the option 'spin=2, multiplicity=1'.

they aren't the same. A non-polarized calculation will yield S^2=0,  
Sz=0.
A spin-polarized calculation with "multiplicity=1" will yield Sz=0  
but not
necessarily S^2=0. See for instance J. Phys. Chem. B 105, 11227
(2001) for a nice description of how neglecting to appreciate such
difference may lead to unphysical results.

P.
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222