Frequency-Dependent Polarizability

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chemphysstudent
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Frequency-Dependent Polarizability

Post by chemphysstudent » 25 Jul 2017, 18:21

I'm interested in calculating the frequency-dependent polarizability of a variety of atomic clusters, ranging from diatomic to polyatomic. To start with, I just want to calculate the polarizability of a single diatom. I see there is an example of this in the Dalton documentation, however it leaves me with several questions. First of all, which state is the polarizability that is calculated for? In general, my molecule will include fine and hyperfine structure, in which case there are many states within the ground electronic manifold. Will Dalton calculate the polarizability for every state? Or just the absolute ground state?

kennethruud
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Re: Frequency-Dependent Polarizability

Post by kennethruud » 06 Aug 2017, 14:51

Hi!

I somewhat belated answer, but hopefully nevertheless of some use. By default, Dalton will calculate the polarizability for lowest state of the given spin and spatial symmetry. For molecules with high symmetry, and using MCSCF wave functions to change spin symmetry, quite a few states can determined in this manner.

The polarizability of excited electronic states can be determined in Dalton either by optimizing the given state explicitly using MCSCF wave functions, or as the double residue of the cubic response function. In the latter case, only excited states of the same spin symmetry as the reference wave function can be calculated, but allows you for instance to use DFT. Note, however, that polarizabilities with HF/DFT in Dalton only can be done for closed-shell reference states (or possibly a restricted high-spin open-shell reference state).

You mention hyperfine interactions, and thus I wonder if you mean specific rotational states for the molecules/clusters. Dalton will only calculate polarizabilities for different electronic states, and if you also want to calculate polarizabilities for specific vibrational or rotational states, tools beyond Dalton will be needed. There will of course then also be additional vibrational and rotational polarizabilities that need to be considered.


Best regards,

Kenneth

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