Reliable frequency and Raman for some specific states.

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Dear Niri,

Thanks for your suggestion. I will try the using the module.
Sorry, I am not sure about the details in the question myself and, beg your patience, I will try making it clearer below.

It' said the perturbation algorithm used in frequency calculation such as coupled perturbed Hartree–Fock (CPHF) requires the wavefunction of the system to be the ground state wavefunction under its multiplicity. Otherwise, the lower-energy wavefunction would be seen in the perturbation process and make the obtained frequency not only contain the result of the studied higher-energy state. A stability check for the wavefunction is always suggested before such calculations.
This algorithm seems to be adopted for analytic frequency calculation in some cases. For numerical frequency calculation, the same problem is said may also produce because the change of the structure may induce the wavefunction converge to a lower-energy state. Calculation using TD scheme doesn't have this problem.
But if the states is as described in may last letter that can not be obtained from TD and is obviously not the ground state under a certain multiplicity, can I get reliable frequency results for them in NWChem? The calculation can always run though, I think.

Thanks again for your kind help.

Best regards.
Edited On 5:27:30 AM PST - Mon, Jan 11th 2016 by Jiangwr14


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