EasySpin forum

Hi!
I have two queries; first one may be very naive, but can anyone please let me know how easyspin is calculating the molar susceptibility of a molecule without the knowledge of molar mass and mass density! Any reference on this would be really helpful.

Second query is; why the chimolT vs T plot is changing drastically when full 3x3 g tensor given as input and when principal values are given with Euler gFrame. I believe the values should come same in this two cases. Please let me know where I am going wrong. My code is given below:

clear, clf, clc
cm = 100clight/1e6; % Conversion constant from cm-1 to MHz
B = 100; % mT
T = 0.01:0.05:300; % K
Cr.S = [3/2, 3/2];
Cr.L = [1 1];
Cr.soc = [-17.7; 232.5]cm;
%Cr.D = [0,-24.474]cm;
Cr.g = [1.992813; 1.793090];
Cr.gFrame = [0 0 0;78.8607 19.8848 -89.2224];
%Cr.g = [0.643345 1.850015 0.020856; -1.772939 0.623834 -0.656308;-0.604806 0.187924 1.927663; 0.118414 -0.305717 -0.078879; 1.461836 0.511324 -0.315881;-3.786474 -1.551041 1.782057];
Cr.J = 77cm; % cm^-1 -> MHz
Exp.Field = B;
Exp.Temperature = T;

Opt.Output = 'chimolT';
Opt.Units = 'CGS';
chimolT = curry(Cr,Exp,Opt);

plot(T,chimolT);
xlabel('temperature (K)');
ylabel('molar magnetic susceptibility (K cm³ mol^{-1})');
grid on;

1. Models calculating susceptibilities, do so for the molar values of these quantities. The experimentalist must previously bring the measurements to these quantities by knowledge of sample mass, FW and experimental magnetic field, and also diamagnetic and sample holder corrections. The model is agnostic towards these values.

2. I won't get into why you define a SOC for Cr(III) (which if octahedral should have L=0). I will just focus on the fact that you define either:
   -two isotropic g-factors: Cr.g = [1.992813; 1.793090]
   -or two anisotropic ones whose principal values have nothing to do with the previous isotropic ones. Try diagonalizing the anisotropic g-tensors:

   Code: Select all

   [V1,D1] = eig(Cr.g(1:3,1:3))
   [V2,D2] = eig(Cr.g(4:6,1:3))

   and you will see that D1 and D2 are all over the place.

Other answer to 1.: EasySpin's curry calculates the magnetic susceptibility of an individual paramagnetic center and then multiplies the result by Avogadro's number (avogadro in EasySpin) to obtain the molar susceptibility.