Molcas Forum

LucaBabetto

Member

Registered: 2018-11-21

Posts: 31

Use Atomic orbitals as input for CASSCF

Hello,

I would like to ask if it were possible to use atomic orbitals as input for a CASSCF calculation.

For example, if I want to calculate the CAS(6,6) of benzene for the description of the pi orbitals, first I would call the GUESSORB or SCF module to get the starting orbitals, eventually rotate the molecular orbitals (which are already pi in nature) to be in the active space, and then I would run the RASSCF calculation.

I would like, instead, to tell the program to pick the six 2pz orbitals on the C atoms and use those in the active space, is this something which can be done?

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: Use Atomic orbitals as input for CASSCF

Not directly, because the AO are not orthogonal. But you could manually create an InpOrb file with coefficients (1,0,0,...), (0,1,0,...), ... and let RASSCF fix them, I think that could work.