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