Exp.Molframe and crystal rotation

[Jgoodsell]

I have a series of crystal rotation spectra I am trying to simulate in the P 21/c space group. I've read through the documentation and examples regarding introducing a tilt in order to see more than one of the sites, but I am not quite sure what I am observing. Regardless of the angle I put into Exp.MolFrame I am seeing what looks like one site. I've attached the simulated rotation and the experimental one.

The main difference seems to be that the experimental spectrum shows each of the resonances on every cycle while the simulated shows components. It seems like what I need is to be able to see each set of magnetically inequivalent site and I might just be observing one.

Is there a way to change tilt angles to better match the experimental spectrum or do I need to add a full second spin center with a tensor offset?

The code I am using is:

Code: Select all

Sys1.S = 5/2;
Sys1.g = [2];
Sys1.A = [-245];
Sys1.D = [-2040 -180];
Sys1.Nucs = '55Mn';
Sys1.HStrain = [10 10];
Sys1.gStrain = [0.0005];
Sys1.AStrain = 5;
Sys1.lwpp = 3.5;

Exp.mwFreq = 9.427454;
Exp.Temperature = 5;
Exp.Range = [5 705];
Exp.nPoints = 3501;
Exp.CrystalSymmetry = 'P21/c';
Exp.MolFrame = [ 20 20 30 ]*pi/180;
Opt.Method = 'matrix';
Opt.nKnots = 20;

%Output crystal rot
cori0 = [0 0 0];          % initial crystal orientation
nL = [1;0;0];              % rotation axis along lab x axis
rho = (0:15:360)*pi/180;   % :x: degree increments
cori = rotatecrystal(cori0,nL,rho);

Exp.CrystalOrientation = cori;
Opt.Output = 'separate';         % request each crystal spectrum separately
[x,y] = pepper(Sys1,Exp,Opt);
stackplot(x,y);

[Stefan Stoll]

If you replace Sys1 in our code with a simple S=1/2 test system with anisotropic g

Code: Select all

clear Sys1
Sys1.S = 1/2;
Sys1.g = [2 2.2 2.5]
Sys1.lwpp = 3.5

then it shows that there are indeed 2 sites, since there are 2 lines in each spectrum.

You can also get the spectra due to a single site using Opt.Sites, which is a documented. Here are the possible settings:

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Opt.Sites = 1;  % only first site
Opt.Sites = 2;  % only second site

When you compare the spectra from site 1 and site 2 for your case, you can see that they are different.