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Manuscript Title: Computer generated subgroup-symmetry adapted irreducible representations and CG coefficients of space groups by the eigenfunction method.
Authors: J.L. Ping, Q.R. Zheng, B.Q. Chen, J.Q. Chen
Program title: IR, CGC
Catalogue identifier: ABHE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 52(1989)355
Programming language: Fortran.
Computer: IBM PC, PC/XT, PC/AT.
Operating system: MS-DOS (PC-DOS) VERSION 2.0 OR HIGHER.
RAM: 256K words
Word size: 16
Peripherals: disc.
Keywords: Space group, Irrep, Cg-coefficient, General purpose, Algebras.
Classification: 4.2.

Nature of problem:
The program computes the characters, subgroup-symmetry adapted projective (both single- and double-valued) irreducible representations (irreps) of the little co-group and the ground representations, the wave-vector selection rules, the Clebsch-Gordan (CG) series and CG coefficients in 230 space groups. The program can also be used for computing the characters, irreps and CG coefficients of the 32 point groups.

Solution method:
The character, single or double-valued irreducible matrix elements and CG coefficients of space group are obtained by solving the eigenequation of the CSGO-I, -III, and -II of G in the class space, group space and Kronecker product space, respectively. The irreps and CG coefficients are subgroup-symmetry adapted. The subgroups are either specified by user or computer.

The program is designed for any space group, for any value of k in the first Brillouin zone.

Unusual features:
Every thing can be computed ab initia without the input of any complicated results. The tables for characters, irreducible represen- tations and CG coefficients are printed out in an easily recognizable form borrowed from Neto's program but with the improvement that exact values (p/q)**1/2 exp(i n/m) instead of decimals are given for the entries.

Running time:
Typical case of moderate complexity require several minutes.