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"Invalid spatial symmetry!" problem in CCSD(T)

7 years 7 months ago #205 by mradon
Dear All:

I am trying to perform CCSD(T) calculations for an open-shell system based on UHF reference under the D2h symmetry. In my MINP file, I used the following keywords to define spin multiplicity, occupation numbers, and spatial symmetry of the required electronic state: mult, symm, occ. I am pretty sure that I used these keywords properly because the SCF converged to the desired electronic state and the energy is the same as computed with other program using the same basis set and geometry.

However, when going to the CC part, the progam gives the following error message and quits:

CC(2)(3) calculation
Number of alpha electrons: 28
Number of beta electrons: 24
Spin multiplicity: 2
z-component of spin: 2.0
Invalid spatial symmetry!

I do not understand why the spatial symmetry is invalid for the CC because it is correctly specified and the same input was OK for the SCF calculations. Moreover, the numbers of alpha and beta electrons printed above is wrong and inconsistent with the ones used during the SCF. Hence, the multiplicity is wrong: 2 should be 6 (five unpaired electrons), the z-component of spin is 2.0, should be 2.5 (BTW, the spin multiplicity 2 and z-component of spin 2.0 are inconsistent with each other).

My question is then: how can I pass the information about spin multiplicity and spatial symmetry to the CC program appropriately? Apparently, the keywords: mult, symm, and occ which work for the SCF part are not respected by the CC part. Should I use some additional keywords to define my wave function properly?

Thank you in advance for any suggestions/ comments!

With best regards,

Dr Mariusz Radon, Ph.D.
Coordination Chemistry Group
Faculty of Chemistry
Jagiellonian University
ul. Ingardena 3, 30-060 Krakow, Poland

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7 years 7 months ago #206 by kallay
Dear Mariusz,
In principle, the reference determinant is the HF determinant, so I don't understand what happens here. If you post the input file, I will take a look at it.
Anyway, you can set the reference determinant using the refdet keyword, that should work even in this case.

Best regards,
Mihaly Kallay
The following user(s) said Thank You: mradon

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7 years 7 months ago #207 by mradon
Thank you! Your solution with refdet works fine.

Best regards,
Mariusz RadoĊ„

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