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Panwang Zhou
pwzhou@gmail.com

Recently I want to do some calculations with MCSCF and XMCQDPT2, and I have some questions related to preparing the start orbitals for MCSCF.

In the refs manual of GAMESS-US, I found the following advises:
1)One way to improve upon the SCF orbitals as starting MOs is to generate valence virtual orbitals (VVOs).  
However, the VVOs is not implented in firefly. Can I reuse the calculated VVOs by GAMESS-US in firefly?

2)Although they said "Pasting the virtuals from a MVOQ run onto the occupied orbitals of a SYMLOC run (both can be done in the same SCF computation) gives the best possible set of starting orbitals.", I'm confused about this because they also said " An alternative choice, not usually as good, are the modified virtual orbitals (MVOs)."

The 3rd question: Can I use the converged DFT orbitals as the start orbitals for MCSCF?

Best Regards!

Panwang Zhou