Simulation with two spin centers that are tilted with respect to each other

[motty]

Hello,

I have a question how to use commands concerning "Exp.MolFrame".

I would like to simulate EPR spectra of a two-spin-system in which two doublet spins are coupled weakly
in solid state in random orientation by using "pepper". The two spins are tilted
with respect to each other but mutual distance and angle are fixed. I have to consider J and d.

Under these conditions, the molecular axes are not parallel. On the other hand, the axis if the dipole-dipole coupling
(only D is none zero but E=0) is parallel to the vector combining two spin centers.

(1) I want to set gframes for spin 1 and that of spin 2 differently as well as A frames.
I found a previous topic tilted "Simulating Two Molecules" on Jun 09, 2016
and the answer was " we can use Exp.MolFrame" but I could not found how to
specify mol.frame of spin1 and spin2 differently in documentations.

There is a description for crystal orientation for two spins.
Exp.CrystalOrientation = [0 0 0; 0 pi/4 0];
For MolFrame, can we use it similar to Exp.CrystalOrientation ?
I would like to know exact how to use command.

(2) I would like to know how I should set D, in terms of command and axis
a)Can I use Sys.D command ? or I should use Sys.eeD ?
(dipole -dipole coupling is between the two doublet spins )
b) With respect to what axis , can I set the frame of the principal axis of D ?
In other words, I have two ideas
one is : I set the mol.Frame of spin 1 is the same as crystal frame
and I set the frame of D respective to mol.Frame of the spin1
the other is : I set both of the mol. Frames of spin 1 and spin 2 that are different from the crystal frame
but the Z axis of D is just parallel to X axis of the crystal axis

I appreciate your advise,
Thanks in advance

Motty

[Stefan Stoll]

It sounds like you need to use Sys.S = [1/2 1/2] (or other spin), and then Sys.gFrame, Sys.AFrame, and Sys.eeFrame to specify the orientations of all tensors.

[motty]

Dear Stefan,
cc.Dear all,

Thank you very much for your advice.
In my system, spin 1(S=1/2) and spin 2(S=1/2) are equivalent and
two electrons are almost localized in each site.
First I thought I just use Exp.MolFrame like.
Exp.MolFrame = [0 pi/2 0; 0 pi/4 0];
with fixing crystal axis to parallel to dipolar axis of the two spins.
(Is the above syntax correct ?)

I will consider to use Sys.gFrame, Sys.AFrame, too.

Many thanks,

Motty