# 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)

## Arguments

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 - optimised magnetic susceptibility tensor in cubic Angstroms. pred_pcs - predicted pseudocontact shift at each nucleus with the optimised mxyz and chi, ppm.

## Examples

See the pseudocontact shift analysis tutorial for a detailed walkthrough.

## See also

ppcs.m, ippcs.m, lpcs.m, ilpcs.m, kpcs.m, ipcs.m, xyz2pms.m

*Version 2.4, authors: Elizaveta Suturina, Ilya Kuprov*