RICC2 - does exsist any "broken symmetry"-like keword in turbomole?

Started by Matteo Guglielmi, November 12, 2007, 03:46:34 PM

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Matteo Guglielmi

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.

christof.haettig

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