[molpro-user] Number of electrons in MRCC

[Hyungjun Kim]

Dear Molpro developers,


I have reported the same problem to the MRCC forum and the developer of MRCC, Mihaly Kallay, suggests me to report this error to Molpro developer.


This is my post on the MRCC forum.


***
I have tried to calculate the electronic structure of Zr atom using CCSDT in MRCC program interfaced to Molpro. Stuttgart ECP is employed during this calculation. (Therefore only 12 electrons are left.)

I have symmetrized HF orbitals and have done CCSDT calculation using these orbitals.

While 4s and 4p orbitals are left as core electrons, 2 electrons in 5s, and 2 electrons in 4d orbitals are distributed, respectively.

When MRCC reads CASSCF MO, there are 4 electrons.
Frozen orbitals: 4 ( 1 1 1 0 1 0 0 0)
Active orbitals: 6 ( 3 0 0 1 0 1 1 0)
Active electrons: 4
Spin quantum number: 1.0

However, the output created by MRCC gives there are only 2 electrons (1alpha and 1beta).
Number of alpha electrons: 1
Number of beta electrons: 1

I don't know why the number of electrons is reduced from 4 to 2. Could you give me a guide to include '4d' electrons in MRCC calculation?

Any comments are welcome.

Yours sincerely,
***


The reply of Kallay to this question is as follows:
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Dear Hyungjun,
The occupation vector and the specification of active orbitals passed over to mrcc is not correct. You should contact the molpro developers about this issue. The quick solution is to specify the directory where mrcc is executed, that is, the corresponding line in the molpro input should be extended, e.g., as
{MRCC,method=CCSDT,spatial=1,HF=0,nacto=0,dir='/scr/mrcc';
Then the scratch files required by mrcc will be saved to that directory. To correct the error edit file fort.56, and replace the last two line by the following ones:
2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 0 0 0
Then execute dmrcc in that directory. Note that in this case an MRCCSDT calculation will be run. If you want to perform a simple CCSDT calculation, the last line of fort.56 must be deleted.
***


I have fixed the problem referring to Kallay's comment.


Could you please check this problem?


Yours sincerely,


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