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Manuscript Title: A program for the calculation of the positions of X-ray powder reflections.
Authors: I.F. Ferguson, R.S. Fox, T.E. Hughes
Program title: FIREBIRD 2
Catalogue identifier: AAQD_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 12(1976)305
Programming language: Fortran.
Computer: ICL 4-72.
Operating system: J 1700.
RAM: 291K words
Word size: 4
Keywords: Crystallography, X-ray, Powder diffraction, Bragg reflection, Positions, Interplanar angles, Indexing, Space groups, Laue groups.
Classification: 8.

Nature of problem:
The program, FIREBIRD, calculates the position of Bragg reflections in X-ray powder diffraction for all crystal systems and Laue groups for a given set of crystal lattice parameters. The general conditions which limit the possible reflections from any space group are allowed for. The program can vary the lattice parameters systematically and since provision is made for comparing the position of calculated and observed Bragg angles FIREBIRD can, in principle, aid in the assignment of Miller indices to any (single phase) X-ray powder diffraction pattern. The program can also be used to generate interplanar angles, crystallographic densities and can produce lists of Miller indices in a form suitable for transcription as input to the program FIREFLY.

Solution method:
All the calculations described are carried out using standard X-ray powder diffraction formulae; where necessary, X-ray reflections not allowed by the general space group symmetry are suppressed.

Restrictions:
The program is restricted to the output of data which relate to 1000 permitted Bragg reflections. In the case of the triclinic and rhombohedral crystal system FIREBIRD only considers the first 10,000 computed Miller indices before output is commenced. No more than 17 different wave-lengths can be handled in any example.

Unusual features:
Some non-standard FORTRAN statements are used including RETURN n to provide alternate return points from subroutines.

Running time:
1 min for a typical example.