Mulliken population analysis at the coupled cluster level
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Mhmd Al ahmad
Feb 23, 2024, 3:38:10 PMFeb 23
to dirac-users
Dear Dirac users
I was doing an optimization calculation on the coupled cluster level. Because I wanted to know the energies of the orbitals, I activated the ANALYZE module. I noticed in my output that the Dirac printed the orbitals' energies two times, first before CC outputs and the second after it. I was expecting that the first would be the Mulliken analysis according to the HF code, while the second according to the CC code, however, the two were identical. another thing, when I do a single point calculation on the coupled cluster level, Dirac prints the energies of the orbitals once time before printing outputs of the coupled cluster code.
Any help or insights on this matter would be much appreciated.
Best regards,
Mohamed.
I was doing an optimization calculation on the coupled cluster level. Because I wanted to know the energies of the orbitals, I activated the ANALYZE module. I noticed in my output that the Dirac printed the orbitals' energies two times, first before CC outputs and the second after it. I was expecting that the first would be the Mulliken analysis according to the HF code, while the second according to the CC code, however, the two were identical. another thing, when I do a single point calculation on the coupled cluster level, Dirac prints the energies of the orbitals once time before printing outputs of the coupled cluster code.
Any help or insights on this matter would be much appreciated.
Best regards,
Mohamed.
Visscher, L. (Luuk)
Feb 26, 2024, 2:53:58 AMFeb 26
to dirac...@googlegroups.com
Dear Mohamed,
The orbital energies printed in RELCCSD are the diagonal elements of a Fock matrix computed with the UNRESTRICTED formalism. If you have a closed shell system these should be identical to the restricted formalism that is used in the SCF and the
printing (by default suppressed when there are no differences) is only a check on correctness of the input. If you have an open shell system, the two lists are different and give information about the size of spin polarization effects.
Luuk
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