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Manuscript Title: A program for the calculation of X-ray reflection intensities, Part 2.
Authors: I.F. Ferguson
Program title: FIREFLY IV
Catalogue identifier: AAQB_v2_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 10(1975)42
Programming language: Fortran.
Computer: ICL 4-72.
Operating system: 4J.
RAM: 391K words
Word size: 8
Peripherals: magnetic tape.
Keywords: Crystallography, Intensities, X-ray, Powder diffraction, Structure-factor, Crystal-structure, Dispersion correction.
Classification: 8.

Subprograms used:
Cat Id Title Reference
AAQB_v1_0 FIREFLY II CPC 5(1973)328

Nature of problem:
The program, FIREFLY IV, an extension of FIREFLY II,calculates the intensities of X-ray reflections with especial reference to the powder method. The program is very flexible and allows the intensity of reflections with given Miller indices to be calculated if the unit cell and its contents are specified together with the equipment used and, if necessary, temperature and absorption factors. Provision is made for the comparsion of observed and calculated data. The most significant differences from FIREFLY II are that FIREFLY IV can: automatically centre the atoms in the unit cell, deal with fractional co-ordinates and, most important, apply a dispersion correction to the calculated intensities.

Solution method:
The Bragg reflection intensities are calculated by the standard formulae of X-ray diffraction as applied to X-ray powder diffraction.

Restrictions:
The program is written to manipulate up to 999 sets of Miller indices, 2000 atoms with coordinates xn', yn and zn, not greater than 100 atom types, 10 wavelengths and up to 9990 observed intensities and angles.

Running time:
5 s for a typical example.