[molpro-user] Degeneracy in MRCI calculation

[Hyungjun Kim]

Dear Molpro users,


I have tried to get MRCISD energy and spin orbit coupling (SOC) for 3F (term symbol) Hf atom. (Electronic configuration of Hf atom is 6s2, 5d2)


MRCISD energy with the active space of 5d and 6s is obtained without an accurate degeneracy.
(7 states, (1Ag, 2B1g, 2B2g, 3B2g) should have the same energy.)


I have a similar problem for Y atom (5s2 4d1) case, and the problem can be solved according to the Peterson's advice to increase an active space.


The increased active space for Hf atom including 5s (which is semi core orbital) gives the improved result. The energy difference is reduced to 10^-6 scale but the energy level of 3F are not still perfectly degenerate.


Could you provide me to recover the degeneracy in MRCI calculation?


Any comments are welcome.


Best regards,


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