From Spinach Documentation Wiki
Packs multipole moments from a linear stream into a cell array that is arranged by ranks.
ranks - a vector of spherical ranks present, e.g. [0 1 2] moments - a vector of multipole moments for each rank, arranged in a linear stream
Ilm - a cell array of vector corresponding to the multipole moments defined in http://dx.doi.org/10.1039/c6cp05437d for L=0, one element for L=1, three elements for L=2, five elements et cetera.