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Manuscript Title: Slit height smearing correction in small angle X-ray scattering II: computation of the correction function.
Authors: M. Deutsch
Program title: FFITEX
Catalogue identifier: AASC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 17(1979)345
Programming language: Fortran.
Computer: IBM 370/168.
Operating system: OS/VS2.
RAM: 9K words
Word size: 32
Keywords: Crystallography, x-ray, Scattering, Diffraction, smearing, Slit, Small-angle.
Classification: 8.

Nature of problem:
The author's exact solution of the slit height smearing problem in small angle X-ray scattering and its implementation, require the use of a correction function g(t) in the correction formula. The parameters defining this function are obtained by fitting an appropriate analytic form to the measured values of the transmission function f(t) of the slit system used in the scattering experiment. The present program performs the required fit and calculates the fit parameters.

Solution method:
The fit is done by minimizing the sum of the squares of the differences between the measured transmission function values, and the values of the parameterized analytic function. The method used is a version of the variable metric method which does not require linear search, and consequently is very fast. The output of the program is the set of fit parameters.

Restrictions:
Only 200 measured values of the slit height transmission function can be handled by the present version.

Running time:
About 1.4 s for 140 transmission function values.