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Re: mcscf in a protein environment

Alex Granovsky

Dear alex,

On Thu Sep 18 '14 1:03am, alex wrote
>Dear Qchemists,
>May I ask you three more questions? The three are related to role of protein environment in a chemical reaction.
>1) Is it possible to consider one part of the system with RHF and another with MCSCF wave functions (suggesting their overlap is vdw only)?

No it's impossible at present.

>2) Is it possible to precalculate coulomb potential/density as a mesh in a sort of cube (like for viewers) for one fragment and then consider this like an external potential during mcscf run of a second system in the cube?

A bit different, but virtually very similar thing is possible indeed.
E.g. one can use EFP approach to model the rest of a protein.

>3) Although mcscf is not capable to deal with entire system, GVB is so-so doable. However to model the reaction in that way I need to transfer an electron from DOC into SOC orbital (from a carbon double bond onto oxygen of a triplet molecule). GVB is usually considered for different application so I am wonder if such migration is feasible with GVB wave functions and if so, can you please advise how to setup such run.

Are you sure MCSCF job is impossible for your system? Firefly
has very efficient MCSCF code that is capable to handle large
systems very efficiently. If it is possible to perform GVB
run then it is very likely that MCSCF run is also possible.

See Firefly's manuals at

for documentation on MCSCF. You can also find some information here:

Kind regards,
Alex Granovsky

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