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ABFfit

The Computing for Science (CS) group supports ILL scientists, students and visitors in a number of activities including data analysis, instrument simulation and sample simulation.

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ABFfit

A profile fitting program for neutron powder diffraction patterns

by A. Antoniadis, J. Berruyer and A. Filhol

 

ABFfit is based on a maximum likelihood algorithm [1]. Powder diffraction patterns are fitted with a mathematical function (peaks+background) without assuming any physical model for the diffraction process.

The maximum likelihood  is the natural analog of least-squares refinement for the Poisson situation (diffraction data are counts), and indeed for all generalized forms of data fitting. For Poisson or generalized Poisson statistics, the maximum likelihood estimates are obtained through the use of iteratively reweighted least squares. In this maximum likelihood model, the weights are determined by the fit whilst with true weighted least squares the weights determine the fit. Our algorithms comprises an estimation procedure for Poisson regression models, measures of the goodness of fit, generalized residuals, diagnostic plots, confidence regions, etc.

ABFfit was very much used for the processing of neutron diffraction data at the ILL and elsewhere. It also served for researches in new data processing algorithms [2]. It was commercially available from the University Jean Monnet of St Etienne until late 2002. It is no longer supported by the CS group.

The program was developped for Mac OS classic [3], VAX/VMS [4] and Unix and exists in many versions.

 

ABFfit for Mac OS

The Mac OS 9 version of ABFfit offers many advanced fitting tools. It was developped in Pascal. Unfortunately this language is no longer supported by Apple and thus there is no Mac OS X version currently available.

However, tools like SheepShaver (Unix, Mac OS X) makes it possible to run ABFfit on todays computers.

Animation of refinement iterations for a simulated typical diffraction pattern.
Solid line: starting pattern; dotted line: theoretical pattern; crosses: simulated data (a realisation of poissonnian variables).


Download the User's manual [3] of ABFfit v4, English version, from HERE (4.1 Mb, 70 pages)

Download the User's manual [3'] of ABFfit v4, French version, from HERE

Download notes about ABFfit v4.9.3 (in French) from HERE

ABFfit for Unix

This is a less advanced version but which can run in automatic mode for sequential refinements. This is especially useful for Time Resolved Diffraction and is routinely used on some ILL powder diffractometers such as D1B.

Input   => myfile.d1b prepared by TEKD1B       

            => FILnnn.dat prepared by FILD1B for sequential refinements      

            => myfile.dom list of angular ranges in degrees 2theta (free format)

Output => ABFFIT.LPT  Contains all results of refinements  

            => myfile.ABF Condensed output file and starting control file for sequential refinements       

            => FILABF.RES The results of sequential refinements          

FIL is the code name (3 letters given by user) for sequential data prepared by FILD1B.

 

Get the source code for ABFfit for Unix from HERE (A. Bouvet, 1998).

 

Bibliography

 

[1]- Maximum-likelihood methods in powder diffraction refinements
      Antoniadis A. Berruyer J. Filhol A. (1990) Acta Crystallographica A 46, 692-711.

[2]- Estimation semi-parametrique dans les familles doublement poissonniennes et application aux spectres de diffraction
      Antoniadis A. Berruyer J. Filhol A. (1999) Revue de Statistique Appliquee 47, 57-80.

[3]- Maximum likehood refinement of powder diffraction patterns
      Antoniadis A. , Berruyer J. , Filhol A. (1987) ILL technical report, ILL90AN08T

[3']- Affinement de spectres de diffraction de poudre
      Antoniadis A. , Berruyer J. , Filhol A. (1987) ILL technical report, ILL90AN08T

[4]- "ABFfit for the Vax. A maximum likehood profile refinement program for poissonnian patterns. Manual for the version 3.0"
      Filhol A. , Blanc J.Y. , Antoniadis A. , Berruyer J. (1988) ILL technical report, ILL88FI5T.

[5]- "ABFfit : Manuel de la version 3.0 pour le MacIntosh"
      Antoniadis A. , Berruyer J. , Filhol A. (1987) ILL technical report, ILL87AN22T

[6]- "Affinement de spectres de diffraction de poudre par la méthode du maximum de vraisemblance"
      Antoniadis A. , Berruyer J. , Filhol A. (1986) ILL technical report, ILL86AN2T

 

Created: 3 Oct 2008, Last update: 6 Oct 2008, A. Filhol <filhol(at)ill.eu>