# Chi eff.m

From Spinach Documentation Wiki

Finds the optimal magnetic susceptibility tensor that a user-supplied paramagnetic centre probability density must have in order to fit the PCS data supplied. Syntax:

[chi,pred_pcs]=chi_eff(source_cube,ranges,nxyz,expt_pcs)

Parameters:

source_cube - paramagnetic centre probability density cube ranges - a six-element vector giving the extents of the probability density cube in Angstroms as [xmin xmax ymin ymax zmin zmax] nxyz - nuclear coordinates as [x y z] with multiple rows, at which PCS is measured, in Angstroms. expt_pcs - pseudocontact shift in ppm at each nucleus.

Outputs:

chi - optimized magnetic susceptibility tensor in cubic Angstroms.

pred_pcs - predicted pseudocontact shift at each nucleus with the optimized mxyz and chi, ppm.