The Zoef approach to Solid Spherical Harmonics
Norbert Ligterink, Control Engineering, University Twente, The Netherlands,
SHY My Fortran code for calculating spherical harmonics.
There are in principle no limits on L and M (Abs(M) LE L). At the
moment the array limit is set at 256 terms in the polynomial,
which corresponds to L=30 for small M and L=22 for M=11 or so.
It is of little consequence to make the arrays much bigger.
It consists of a number of subroutines:
Y generates
a list of terms which is a polynomial in x, y, and z, of a
normalized solid spherical harmonic r^l Y_lm.
PRNTY prints a spherical harmonic to be used
in other codes.
MATEL calculates the matrix elements
< L,M| x^k y^n z^p |L',M'> fast with typical 14-15
decimals precision (for orthogonality, a couple less for
general matrix elements).