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Manuscript Title: XFIT: a package for simulating and fitting X-ray powder diffraction patterns.
Authors: A. Martorana, R. Gerbasi, A. Marigo, R. Zannetti
Program title: XFIT
Catalogue identifier: ACKY_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 34(1984)145
Programming language: Fortran.
Computer: CYBER 76.
Operating system: NOS/BE 1.3.
RAM: 56K words
Word size: 60
Peripherals: disc.
Keywords: Solid state physics, Experiment, Diffraction powder, Data fitting, Structural model.
Classification: 7.4.

Subprograms used:
Cat Id Title Reference
ABCH_v1_0 GSFIT CPC 8(1974)56
ACWH_v1_0 MINUIT CPC 10(1975)343

Nature of problem:
A structure hypothesis relative to a powder, a polycrystalline or a glassy material can be tested by comparison between the experimental X- ray powder pattern and a calculated one.

Solution method:
XFIT consists of three programs: PROVA 2, GSFIT2 and MINUITS. PROVA 2 generates the calculated patterns by evaluation of one surface integral for each calculated intensity; GSFIT2 converts into analytical form the dependence of the calculated patterns on the structural parameters; MINUITS (by the supported FCN subroutine) optimizes the structural parameters to achieve the best fit to the experimental pattern. GSFIT2 and MINUITS may be called as subroutines by PROVA2 or run separately as independent programs.

Restrictions:
The dimensioning of the arrays allows up to 100 intensity values and 6 structural parameters to be handled.

Running time:
Depending on the complexity of the proposed structural model; the one presented in the test run requires 1.75 seconds per intensity value.