EasySpin forum

Posted: **Sun Sep 07, 2014 9:42 am**

I'm currently trying to find the orientations of some non-principle axis transitions from a set of powder data using esfit... with no success. Is this something that can be done using easySpin? I've tried isolating the data to a specific transition, but no matter what value I set the orientation to, esfit spits out the exact same number. For example, if I set Sys.Orientations = [0 0], esfit outputs 0 and 0... if I set the Orientations to [pi/8 pi/8], esfit outputs pi/8 and pi/8 and so on. So no fitting is truly being done.

My code is pretty simple:

Code: Select all

clear

%Load Tab Spaced File
%X column is mT
[B,spc] = textread('206.4GHz Cut.txt','%f	%f');

%Defining Parameters
Sys.S = 2;
Sys.D=[-96993.9851  1931.4];
Sys.g = [2.0, 2.0, 2.0];
Sys.lw = 63;
Sys.Orientations = [0 0];

Exp.Range = [9000 11000]; %Narrowed down transition to specific range
Exp.mwFreq = 206.4;
Exp.Temperature = 11;

%Define parameters to be fit (with variation range)
Vary.Orientations = [2*pi, pi];

bestSys = esfit('pepper', spc, Sys, Vary, Exp);

Thanks in advance any help/advice!

Posted: **Sun Sep 07, 2014 3:59 pm**

So your first problem is that Sys.Orientation doesn't actually do anything. A simple check is to feed your system and experimental into pepper and try to manually vary Sys.orientation, you'll see it has no effect on the simulation.

Now if I understand you right you're looking to identify a specific transition(orientation of the ZFS with respect to the lab frame) which contributes to your spectrum. The parameter you're looking for is Exp.orientation = [phi;theta;chi], where this would compute a single crystal orientation. The problem is within the context of EasySpin we can't actually fit that parameter.

One possible work around is to use Exp.Orientations and fix the magnetic field along a specific axis then to fit Sys.Dpa which would be the orientation of ZFS Tensor with respect to the lab field at the fixed orientation.

So something like:

Code: Select all

clear

%Load Tab Spaced File
%X column is mT
%[B,spc] = textread('206.4GHz Cut.txt','%f   %f');

%Defining Parameters
Sys.S = 2;
Sys.D = [-96993.9851  1931.4];
Sys.g = [2.0, 2.0, 2.0];
Sys.lw = 63;

Sys.Dpa = [0*pi/4 0*pi/4 0*pi/4];

Exp.Orientations = [0; 0; 0]; % crystal with z axis aligned with B0
Exp.Range = [9000 11000]; %Narrowed down transition to specific range
Exp.mwFreq = 206.4;
Exp.Temperature = 11;

%pepper(Sys,Exp)

%Define parameters to be fit (with variation range)
Vary.Dpa = [pi/2, pi/2 pi/2];

esfit('pepper', spc, Sys, Vary, Exp);

Posted: **Mon Sep 08, 2014 8:05 am**

Wow this works perfectly thanks!

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