[molpro-user] CAS with wrong configuration of HF

[SungHwan Choi]

Dear all,
Hi, I am now trying to compute the energy difference between high spin
state and low spin state of octahedral metal complex with CAS level.

The problem that I am struggling is that the HF method does not give a
proper configuration even in singlet state. The d orbitals are completely
occupied and also some ligand orbitals are above them. It is difficult to
generate the electronic structure with the correct configuration with HF.
In this case, may I set the active space of CAS as fully occupied orbitals
with 6 electrons? or is there any other way to make the correct electronic
configuration with HF?

The case that I am trying is quite simple one. Here is my target geometry

13

Fe       0.000000    0.000000    0.000000
C        0.000000    0.000000    2.003402
C       0.000000    2.003402    0.000000
C      -2.003402    0.000000    0.000000
C       0.000000   -2.003402    0.000000
C       2.003402    0.000000    0.000000
C       0.000000    0.000000   -2.003402
O       0.000000    3.187907    0.000000
O       3.187907    0.000000    0.000000
O       0.000000    0.000000    3.187907
O      -3.187907    0.000000    0.000000
O       0.000000   -3.187907    0.000000
O       0.000000    0.000000   -3.187907


Sincerely
Sunghwan Choi
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