Ppcs.m

Point electron pseudocontact shift model.

Syntax

    pcs=ppcs(nxyz,mxyz,chi)

Description

This function computes pseudocontact shifts from a point electron with user-supplied coordinates and susceptibility tensor at the nuclear coordinates supplied.

Arguments

    chi     - electron magnetic susceptibility tensor in cubic 
              Angstroms as a 3x3 matrix, or its five unique 
              components ordered as
                
               [chi(1,1) chi(1,2) chi(1,3) chi(2,2) chi(2,3)]

    nxyz    - nuclear coordinates as [x y z] with multiple rows,
              at which PCS is to be evaluated, in Angstroms. If
              a cell array of such specifications is supplied,
              the average PCS over them is returned.

    mxyz    - paramagnetic centre coordinates as [x y z], in 
              Angstroms.

Returns

    pcs     - predicted pseudocontact shift (in ppm) at each of 
              the nuclei.

Examples

The following example is available in nmr_paramag/porphyrin_example_1.m function in the example set supplied with Spinach:

    function porphyrin_example_1()
    
    % Porphyrin ring proton coordinates
    nxyz=[ 4.551635888      2.658552774      0.000000000
           2.658552774      4.551635889      0.000000000
          -2.658552774      4.551635888      0.000000000
          -4.551635889      2.658552774      0.000000000
          -4.551635888     -2.658552774      0.000000000
          -2.658552774     -4.551635889      0.000000000
           2.658552774     -4.551635888      0.000000000
           4.551635889     -2.658552774      0.000000000
           4.533874147      0.000000000      0.000000000
           0.000000000     -4.533874147      0.000000000
          -4.533874147      0.000000000      0.000000000
           0.000000000      4.533874147      0.000000000];

    % Co(II) g-tensor eigenvalues
    g_co=diag([3.0 3.0 2.0]);
    
    % Cu(II) g-tensor eigenvalues
    g_cu=diag([2.0 2.0 2.2]);
    
    % Curie susceptibility tensors
    chi_co=g2chi(g_co,298);
    chi_cu=g2chi(g_cu,298);
    
    % Metal position 
    mxyz=[0 0 0];
    
    % PCS calculation
    point_pcs_co=ppcs(nxyz,mxyz,chi_co);
    point_pcs_cu=ppcs(nxyz,mxyz,chi_cu);
    
    % Output
    disp('Pseudocontact shifts [Co, Cu], ppm');
    disp([point_pcs_co point_pcs_cu]);
    
    end

Notes

Point model fails for nuclei positioned closer than about 10 Angstroms to the paramagnetic centre. For room temperature systems, it is possible to convert the g-tensor into the susceptibility tensor using g2chi.m function.

See also

kpcs.m, ippcs.m, lpcs.m, ilpcs.m, ipcs.m

Version 1.9, authors: Ilya Kuprov, Elizaveta Suturina