Indirect Spin-Spin Coupling Tensors

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Dear admins and users,

While calculating indirect spin-spin coupling constants, we noticed that:

(1) For closed-shell systems, one has to specify UHF wave function. For example, using DFT, one needs to include ODFT in the DFT block. Otherwise, the spin-spin coupling calculations will be skipped with the following message:

     Indirect spin-spin coupling not calculated for RHF
wave functions: needs UHF wave function

(2) For open-shell systems containing unpaired electrons, the calculations won't run, showing the following message:

     Indirect spin-spin coupling not calculated for open
shell wave functions: needs closed shell UHF!

By "closed shell UHF", it probably means the current version is only implemented for closed-shell system and in order to run, one needs to use UHF wave function.

Questions: Is spin-spin coupling not implemented for open-shell systems? Is that because it simply does not make much sense to study spin-spin coupling for open shell systems? Or is it because the unpaired electron already makes the situation complicated (i.e. p-NMR)? Or could it be that the small J coupling (on the order of Hz) is overwhelmed by the large hyper fine coupling (on the order of MHz) due to the presence of an unpaired electron? I don't have much experience with NMR for open-shell systems so these are some key questions for us at the moment.


Edited On 1:55:21 PM PDT - Tue, Mar 29th 2016 by Huangj3

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