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