PROGRAM SUMMARY
Title of program:
369j
Catalogue identifier:
ADKL
Ref. in CPC:
120(1999)222
Operating system: UNIX (Digital)
Number of bits in a word:
64
Number of lines in distributed program, including test data, etc:
1450
Programming language used: Fortran
Computer: DEC 3000/400 alpha
Nature of physical problem:
Angular momentum coupling and recoupling coefficients occur in almost
all of the areas using quantum mechanics. The accurate and fast
calculation of 3j, 6j and 9j symbols is required in a variety of
situations in nuclear physics, atomic physics, molecular physics, and
astrophysics, etc.
Method of solution
The algebraic expressions of 3j, 6j and 9j symbols have all been
reformulated as the summation of products of binomial coefficients. The
programs calculate the binomial recursively at every stage instead of
evaluating factorials of integers. We also use two different number
representations in the calculation: prime number representation for the
prefactor, and 32768-base number representation for the summation terms.
Typical running time
The time taken for calculating 3j, 6j and 9j symbols of small angular
momenta is almost instantaneous. It is still less than 0.1 second for
3j symbols, and 0.2 second for 6j symbols, when angular momenta reach
200. For 9j symbols, it is less than 1.0 second when angular momenta
approach 100.