Different CC energy with localized orbitals

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10 months 4 days ago #1203 by benedek1231
Dear Developers,

as far as I am concerned, the CC energy should be invariant with respect to orbital localization.
Indeed, if I run CCS or CCSD calculations with localized orbitals (orbloco=pm, orblocv=pm), the energy equals to that from the same calculation with canonical (HF) orbitals.

However, if I run
-higher-order CC (e.g. CCSDT, CCSDTQ), or
- CCSD with ccprog=mrcc
I obtain different energies with and without orbloco/orblocv (which should not be the case in theory).

What is the reason for this, and can it be fixed somehow?

I attach four output files to illustrate the above points. (CCSD with/without orbloc with same energy; CCSDT with/without orbloc with different energy.)

Best,
Zsolt


 

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10 months 2 days ago #1204 by nagypeter
Dear Zsolt,

This behavior is due to the symmetry of your molecule, which is not handled at all in the orbital localization module.
Please, set symm=off for the calculations using localized orbitals and ccprog=mrcc.

Best wishes,
Peter

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