CGC Library


  CGC : Clebsch-Gordan Coupling Coefficients

About CGC

CGC is a small C library and test program for calculating high order Clebsch-Gordan coupling coefficients. Here, high order means principal quantum numbers of up to about 260 in ordinary double precision and 400 or more in long double precision. When using the GMP arbitrary precision math library, there is essentially no limit on the maximum quantum numbers. The code was written by late Dave Ritchie.

CGC was developed on a 64-bit Linux system, but it should be possible to compile it on Mac OS X or Windows. The only external pre-requisite is the GMP multiple precision math library.

Download CGC 1.0.0

CGC is released under the Gnu LGPL licence. This means you can include it in your own code.

CGC 1.0.0  (to be updated, currently not working)

CGC Documentation and Examples

A brief README file is included in the software installation.


The following publication describes the CGC algorithm:

See also another work by G. Xu, using a Python library:


Dave Ritchie passed away prematurely on Sept 15, 2019. His open-mindedness and scientific contributions continue to inspire us.


Sjoerd de Vries
Campus Scientifique
54500 Vandoeuvre-lès-Nancy
sjoerd.devries AT