EasySpin forum

Hello:

I am trying to simulate a spectrum from an ORCA calculation. I followed the steps from the "Importing EPR parameters from ORCA" section on the website and successfully obtained the spectrum of the test molecule. However, when I tried it with my molecule the calculation kept hanging for hours without finishing. Any suggestions?

I am attaching to this my prop file for testing. Thank you very much in advance.
José Manuel

Well you have a couple problems, but the main one is that ultimately the problem is just too big for Matlab and Easyspin to handle.
So how can you fix that:

• Estimate your linewidth, and remove all of the nuclei that fall below that, you can do that when you import the .prop file.

• Remove the (majority)non-magnetic nuclei, namely carbon but also the iron if you're not specifically labelled. If you don't, Easyspin will take into account the isotope ratios and that makes the problem enormous. Use Sys = nucspinrmv(Sys,[indx])

• With the remaining nuclei, change them to the most abundant nuclei

• alternatively for the last two points, you can use Opt.IsoCutoff and increase it a bit(>0.1) from its default

This gives you something like:

clear
Sys = orca2easyspin('sextuplete.prop',mt2mhz(0.2)); % only keep hyperfine above roughly 2 G modulation amplitude
Sys = nucspinrmv(Sys,[1 2 3 4 5 6 7 8]); % remove the largely non-magnetic nuclei
Sys.Nucs = '1H'; % at this level of filtering we only have one nuclei left
Sys.lwpp = 0.2; % set the linewidth based on the above cutoff

Then add on your experimental parameters such as

Exp.mwFreq = 9.5;
Exp.Range = [320 340];
Exp.nPoint = 201;

pepper(Sys,Exp);

You did not simulate any zerofield splitting parameters so the spectrum doesn't look all that exciting even though you are a septuplete.

Dear Dr. Krzyaniak:

Thank you very much for your kind and prompt answer. I now understand much better the easyspin program. Indeed, I forgot to compute the ZFS. I will have to redo the ORCA calculation and try again.

All the best,
JM