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Manuscript Title: A more efficient version of the WEIGHTS and NJSYM packages.
Authors: N.S. Scott, A. Hibbert
Program title: NJSYM - A MORE EFFICIENT VERSION
Catalogue identifier: AAGD_v3_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 28(1982)189
Programming language: Fortran.
Computer: CRAY-1.
Operating system: OS 1.10.
RAM: 38K words
Word size: 64
Keywords: General purpose, Rotation group, Structure, Scattering, Recoupling coefficients, Racah coefficient, 3n-j symbol, Angular momentum, Element matrix, Angular integral.
Classification: 4.1.

Nature of problem:
A general recoupling coefficient for an arbitrary number of integer or half integer angular momenta is calculated.

Solution method:
The recoupling coefficient is first expressed as a sum over products of Racah coefficients multiplied by (-1) factors and (2j+1)**1/2 factors. This summation is then evaluated using an efficient Rach coefficient subroutine which is a factor of six faster than the original one employed in the NJSYM package.

Restrictions:
The program can be used to calculate a recoupling coefficient containing any number of angular momenta by modifying the dimensions of appropriate arrays.

Unusual features:
When the program has been used once to evaluate a given recoupling coefficient it is possible to call the routine over and over again for the same coefficient with different angular momenta without re-expressing the recoupling coefficient in terms of Racah coefficients. This facilty now works in all circumstances (see section 2 of the long write-up).

Running time:
The test run took 0.5 s execution time on the CRAY-1.