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Stefan Stoll wrote:You will have to convert the hyperfine coupling tensor from the uncoupled to the coupled representation. This is covered in textbooks, see e.g. Bencini/Gatteschi, EPR of Exchange Coupled Systems.

Dear Stefan,

Thanks for pointing that out, now it is completely clear to me.

Best,
Ju

Regarding the zero-field splitting term, there is none if you have two coupled S=1/2 spins. There is an effective zero-field splitting term once you treat the system in the coupled basis (i.e. singlet plus triplet, instead of two doublets). Dear Stefan, Thanks for your reply that made the question ...

Hi All, Again, I have a question regarding exchange coupled system when simulating hyperfine splittings. The example case is for biradicals known with strong exchange coupling interactions. I wanted to simulate the hyperfine splittings compare to the spectrum. The normal code for an isotropic simula...

I would say the spectrum does not look like in good quality, I even doubt the fine structures showing on the left peak are really hyperfine splittings. It's better to get a good tuning, lower the scan rate, or run more scan before getting into simulation.

Typically, susceptibility measurements are much less informative than EPR spectra, esp.if the exchange coupling is really small. If you see no difference between the monoradical and the biradical, this is very strong evidence that the coupling is rather insignificant. Dear Stefan, Indeed, I really ...

Be careful to cleanly distinguish between the hf coupling (A in the spin Hamiltonian) and the hf splitting (observed in the spectrum). Here is an example that shows the effect of strong exchange coupling on the hf splitting: clear, clc g = 2; A = 80; Nuc = '1H'; lw = 1; % Individual spin Sys1.S = 1...

What I have learnt is that for an exchange coupled system, the observed A values is roughly half of the intrinsic A values. This depends on the formalism you use. The hf coupling is only halved if you use the coupled representation with S=1. If you use two S=1/2 with isotropic exchange, it is expec...

Stefan Stoll wrote:The bug is now fixed in version 5.2.25.

Thank you Stefan, I updated to this version and this issue was gone.

Yes, I had the same issue with PC when updating from 5.2.12 to the latest version. I downgrade it back to previous version and had no problem. Hope someone can explain this.

The deviation of the simulation form the experiments has two aspects: (a) the exp has a broad underlying line that the sim doesn't capture; (b) there is a slight asymmetry in the experiment that the sim doesn't capture. As for (a), you can attempt to subtract a broad Lorentzian line from the experi...