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Manuscript Title: I. A computer program for normalization and instrument correction of neutron diffraction data on non-crystalline materials to obtain the static structure factor.
Authors: F.Y. Hansen
Program title: FYINT
Catalogue identifier: ACYR_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 15(1978)401
Programming language: Fortran.
Computer: IBM 370/168.
Operating system: OS/VS2, 4MVS.
RAM: 13K words
Word size: 32
Peripherals: disc.
Keywords: Solid state physics, Non-crystalline, Neutron diffraction, Structure factor, Instrument correction, Normalization, Pair distrubution, Fourier transform, Scattering, Experiment.
Classification: 7.4, 7.6.

Subprograms used:
Cat Id Title Reference
ACYS_v1_0 FYPAR CPC 15(1978)417
ACYT_v1_0 PAR CPC 15(1978)431

Nature of problem:
The structure factor of non-crystalline materials may be obtained from neutron diffraction data. After correction for background two important problems remain, namely a proper instrumental correction and a normalization of the experimental data. With this program instrumental corrections for samples with a cylindrical symmetry are calculated, and the data are normalized in a systematic way providing the structure factor for the material. The instrumental corrections include corrections for attenuation of the neutron beam, incoherent scattering, multiple scattering and non-static behaviour in terms of the Placzek correction. The normalization of the data is based on the macroscopic density of the sample.

Solution method:
The multiple scattering is assumed to be isotropic and the calculation of the correction for non-static behaviour is based on an approximate expression, where the specific interactions between atoms are not included. The validity of the expression is best for heavy elements and relatively small wave vector transfers. The data are normalized by a least squares fit calculation to the Fourier transform of the structure factor at small distances r, where it is given by the macroscopic density of the sample.

Restrictions:
The calculation of multiple scattering and attenuation of the neutron beam is restricted to a cylindrical symmetry, and the data have to be corrected for background. The experiment should be performed in such a way as to make the Placzek correction as small as possible.

Unusual features:
The storage requirement depends on the number of experimental data and the number of neutron wave lengths used in the experiment. In the present set up the storage requirement is set to 13337 words, which are estimated to be satisfactory for a large number of cases.