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Manuscript Title: A computer program written in Mathematica for calculating H2 quasicrystals and their diffraction patterns.
Authors: R. Grodzicky
Program title: QCDiffractor
Catalogue identifier: ADNU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 136(2001)236
Programming language: Mathematica.
Keywords: H2 quasicrystals, Quasicrystal diffraction, Mathematica, QCDiffractor, Crystallography.
Classification: 8.

Nature of problem:
Generation of quasicrystal images and their X-ray diffraction patterns.

Solution method:
The desired quasicrystal fragment is obtained and drawn using a "cut and project scheme". Each point (atom) of the quasicrystal fragment is replaced by a delta function such that its "spike" has the same coordinates as the corresponding quasicrystal point; the (finite) sum of all such delta functions is taken, and the Fourier transform of the sum is then calculated; taking the square of the modulus of the abovementioned Fourier transform yields the diffraction intensity in the case of a perfectly sensitive detector. One may plot this intensity if one chooses, or introduce a threshold intensity (below which detection is impossible) in order to model an imperfectly sensitive detector.

The time and memory required increase when one augments the resolution of the diffraction image or the number of points in the fragment. The number of points in the fragment is roughly proportional to the area of the fragment region as well as to the area of the window region.

Unusual features:
A threshold diffraction intensity for detection has been incorporated into the program.

Running time:
Several minutes for simple examples; hours or days for more complex cases.