EasySpin forum

Sys.ee includes all forms of electron-electron interactions, no matter what the physical origin is.
Check out the corresponding ES documentation.

Did you mean [-1 -1 2]*270? If yes, this is just the through-space dipolar coupling between two electron spins,
aligned along the z axis.

That's an inaccuracy in the documentation. The termination tolerance for Levenberg/Marquardt is FitOpt.TolStep, but for the simplex it is FitOpt.TolEdgeLength: When the edge length of the N+1-dimensional simplex falls below that number, the algorithm will terminate.

I'll fix the documentation.

Putting some degree of parallelization into ES has been on the to-do list for quite a while. The downside would be that it will require an additional toolbox. I am trying to keep ES running with the (admittedly somewhat feature-anemic) Matlab core.

You are trying to fit N=9 parameters simultaneously. In the simplex algorithm, esfit first computes N+1=10 spectra with slightly different parameter sets within your range to set up what's called the initial simplex. During these setup simulations, esfit does not check FitOpt.maxTime. Only after tha...