TURBOMOLE Users Forum

TURBOMOLE Modules => Ricc2 => Topic started by: Matteo Guglielmi on November 12, 2007, 03:46:34 PM

Title: RICC2 - does exsist any "broken symmetry"-like keword in turbomole?
Post by: Matteo Guglielmi on November 12, 2007, 03:46:34 PM

Hello world,

I would need to perform a ricc2 calculation based on an UHF wave function.
Does anybody know if there is any keword to force a broken symmetry (BS)
approach for the selected (siglet) excited states?

Best,
MG.

Title: Re: RICC2 - does exsist any "broken symmetry"-like keword in turbomole?
Post by: christof.haettig on November 16, 2007, 06:00:37 PM

CC2 is a correlated wavefunction based method. To the best of my knowledge there is
no theory for a BS approach with correlated wavefuntions. In difference to DFT,  one tries
in coupled-cluster methods to build a correlated wavefunction with the correct spin-coupling.
Not that neither CC2 not MP2 are suited or intended to treat systems with several open shells
and multi-determinant ground states.

Christof Haettig