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Re^7: MRCI

Alex Granovsky

Dear Maksim,

>Then, in Molpro for MRCI level of theory I have the energies:
>-52.338309 (4.00 A), -52.338409 (4.10 A) and -52.338304 (4.20 A) and
>energy differences:
>-0.000100 [E(4.10)-E(4.00)] and +0.000105 [E(4.20)-E(4.10)].

>Thus, on passing from CASSCF to MRCI the energy decreases approximately 0.5 a.u. at each point, and minimum shifts from approximately 4.30 A to 4.00 A.

This is only possible if Molpro includes 8 lowest occupied orbitals
as double occupied inactive orbitals in the MRCI procedure.
This means that these orbitals are *not* frozen and that the single
and double excitations from these orbitals are allowed. This is
something I asked you about earlier. Note there are no inactive
orbitals in the SOCI procedure. With Firefly, the simplest way to
include inactive double occupied orbitals is to use XMCQDPT2.

Kind regards,

[ This message was edited on Tue Nov 11 '14 at 2:09pm by the author ]

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