EasySpin forum

Hi,
I have a question about writing the hyperfine interaction on EasySpin program. Any suggestion will be much appreciated!
I'm working on a system containing four spins and I would like to consider the hyperfine interaction just for two of them. Do I have to specify all the nuclei?
I've written the following code:

Sys.S = [1/2 2 2 1/2];
Sys.g = [19.5 2 2 19.5]; % g factors [x,y,z]
D23 = [-1 -1 2]*1.4330e+03;
Dzero = [0 0 0]
Sys.eeD = [Dzero; Dzero; Dzero; D23; Dzero; Dzero];% principal value of dipolar coupling tensor, MHz
Sys.Nucs=['165Ho,55Mn,55Mn,165Ho'];
A=1.00;
Sys.A = [A 0 0 0;0 0 0 0;0 0 0 0;0 0 0 A]*830;
Sys.lwpp = 6; % gaussian line broadening in mT (can make lorenzian too)
[B,spec] = pepper(Sys,Exp); %Pepper runs the simulation (good for powder and frozen solutions)

However, I couldn't run this simulation because it's appearing an error message ''Error in pepper'"

Thanks,
Livia

First, in your code you haven't defined an Exp structure.

After I defined one of my own, the error was related to the size of the Matlab array required. Even with Opt.Method = 'hybrid' it was just as large. Maybe you need to change your Matlab preferences, assuming your hardware permits it. Or maybe there is some other Easyspin optimization I don't know.

Finally, and most importantly, since only the Mn(III) ions are in interaction, why add the Ho(III) ions in your system? Unless there is something I misunderstand, couldn't you just define two systems, one for the Mn dimer and one for Ho? This would dramatically reduce your problem's size.

Hello Thanasis,

Thank you for your suggestion!
It is important to include the Ho ions in the model due to the hyperfine interaction. The splitting which we are seeing in the EPR spectra comes from the interaction between the electron and the nuclear spin of the Ho ions.

If you do not plan on including the couplings to the two 55Mn nuclei, you can just remove them: If you want to include couplings to both 165Ho and both 55Mn nuclei, then the spin system is indeed quite large. hsdim(Sys) gives 230400. That will be tough to fit into any computer's memory. You might want to look into using Opt.Method='perturb' or 'hybrid' to reduce the dimensionality.

In your spin system, it looks like only the second and third electron spin are coupled. You can then simulate the first and fourth separately and then just add the spectra.

Hello Stefan,

Thank you so much for your suggestion!