natural isotopes of equivalent nuclei

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Re: natural isotopes of equivalent nuclei

Postby Stefan Stoll » Fri Sep 08, 2017 8:12 am

If you supply the spin system description, then you can obtain hyperfine information:
Code: Select all
clear
Sys.Nucs = 'Cu,Cl';
Sys.A = [40 15];
Sys.n = [2 4];
out = isotopologues(Sys);
out.A
Stefan Stoll
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Re: natural isotopes of equivalent nuclei

Postby katarkon » Mon Sep 11, 2017 1:53 am

Thanks. It was hard to guess right, but looks naturally.
Now I try to adopt the function isotopologues() for the function exchange() and found an unpleasant restriction that A matrix size should be Nx1, Nx2 or Nx3 only. Larger sizes throws error like this:
Code: Select all
Error using isotopologues (line 311)
Sys.A size (2x4) is inconsistent with number of spins (1 electrons, 2 nuclei).

This prevents to simulate the chemical exchange more than for three sites by natural way. Is it able to make less strict checks for A matrix consistence?
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Re: natural isotopes of equivalent nuclei

Postby Stefan Stoll » Mon Sep 11, 2017 8:00 am

This is an ambiguous input: for a spin system with two nuclei, Sys.A = [5 7; 8 12] could either mean a single site with axial coupling tensor, or two sites with isotropic tensors. Therefore, ES does support chemical exchange at the moment. The input syntax for HFCs would need to be modified, which would be a significant breaking change.

I suggest to run isotopologues on separate spin systems for each site, and then assemble the results into a single spin system structure with combined A.
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Re: natural isotopes of equivalent nuclei

Postby katarkon » Tue Sep 12, 2017 12:07 am

It looks that isotopologues calculates A values by simple multiplying of corresponding row of A matrix on corresponding scale factor. If it so, the A matrix for exchange should be appropriate too, but it should be transorm from A(iSite,iNuc) to A(iNuc,iSite) form. But such matrix will not pass the consistency chek if number of sites will be more than 3.
I propose to simplify the check for consistency and keep only condition that size of the first dimension of A matrix must be equal to the number of nuclei. It seems not to be hard.
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Re: natural isotopes of equivalent nuclei

Postby Stefan Stoll » Tue Sep 12, 2017 5:17 pm

This should be possible in 5.2.2.
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