Points2mult.m

Computes multipole moments from a set of points with user-specified spin populations. Syntax:

    Ilm=points2mult(xyz,mxyz,rho,L,method)

The multipoles in question are described in http://dx.doi.org/10.1039/c6cp05437d

Parameters:

    xyz    - coordinates as [x y z] with multiple rows,
             at which density rho is evaluated, in Angstroms.

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

    L      - array of ranks of spherical harmonics of the density

    rho    - column of the densities at the points xyz

    method - 'points' or 'grid'. If the spin density is supplied 
             as Mulliken spin populations at individual nuclei,
             choose 'points'; if the spin density is supplied as
             a probability on a uniform cubic grid obtained from
             ndgrid() function and vectorised, use 'grid'. In the
             latter case, the point coordinates must also come
             from ndgrid() function.

Output:

    Ilm  - multipole moments of the spin density