Symmetry-dependent answers in open shell RELCCSD

[Alexander Oleynichenko]

Dear DIRAC users and developers,

I'm trying to calculate MP2 and CCSD energy of the open shell nitrogen monooxide (NO) molecule. Basically I'm following the manual (http://diracprogram.org/doc/release-22/tutorials/highspin_cc/O2.html).

It seems rather weird that I obtain different MP2 and CCSD correlation energies in different symmetries (output files are attached):

symmetry   MP2                     CCSD

C1:                -0.34256475      -0.33838921

Cs:                -0.34254696      -0.33828588

C2:                -0.34269326      -0.33838921

C2v:              -0.34269326      -0.33838921

Cinfv:            -0.34269326     -0.33838921

It seems like smth is wrong with the reconstructed Fock matrix and re-calculated diagonal Fock matrix elements. I've also printed transformed one-electron part of the Hamiltonian stored in the MRCONEE file and found that all matrix elements are real and coincide for Cs and Cinfv symmetries except the only one pair of spinors (number 19 and 25, the matrix elements between them is complex in Cs, but real parts are the same as in the Cinfv case).

Please, could you take a look, what can be wrong?

Best regards,

Alexander Oleynichenko

[Ilias Miroslav, doc. RNDr., PhD.]

Hello,

NO has degenerate pi-orbitals (https://www.sarthaks.com/1013489/explain-the-mo-diagram-for-no-molecule  )

Few recalculated diagonal elements are different , as seen on the output  (C1:  -0.2016263919    0.1460295075; C2v:  -0.2016263919    0.1093294917 ) - these are the open shell pi-orbitals.

For degenerate cases like this one please try http://diracprogram.org/doc/master/manual/wave_function/relccsd.html#useoe 

Best,

Miro

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From: dirac...@googlegroups.com <dirac...@googlegroups.com> on behalf of Alexander Oleynichenko <alexvole...@gmail.com>
Sent: Sunday, June 5, 2022 10:51
To: dirac-users <dirac...@googlegroups.com>
Subject: [dirac-users] Symmetry-dependent answers in open shell RELCCSD

 

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