A Rietveld Refinement Program for Real Time Powder Diffraction Patterns XND, Release 1.20

This is now the reference manual, its files can be loaded also as a postcript compressed archive directly or on the ftp server. The old french xnd_doc.d file may contains some details which have not been updated in this documentation. The input file structure was modified in the 1.20 release to allow an easier description of complex phases like composites, however xnd_1.20 can read some files of the previous release.

A short tutorial has been introduced in this manual, it comments an example file.

Contents

• Introduction

The program

• General informations
• Method
• Some definitions
  • Orientation functions
  • Prefered Orientation of the sample
  • Line Profile
  • Excluded regions
• Release information
• The xnd package
• References
• Credits
• Published application examples
• Sources and ftp
• Short Tutorial
• FAQ
  • from scale factors to absolutes intensities and/or phases percentage
• CCP14 Mirrors
• Author

Users Files

• Input file description
  • The header part
  • description of experiments
  • description of phases
  • encoding of variables in standard blocks, usage of codewords
  • 4D-lattice symmetry recognised in xnd
• Symmetry file
• Diffusion tables file
• Ouput file description
• Profile file description
• New file description
• hkl file description
• binary file description
• data files description

Usage and related info

• Exit and error codes
• Cycling xnd and other utilities.
• Examples files

Installation and structure of the program

• Installation guide.
• Structure of the program.

Introduction

The source of the program is written in ANSI C language and great care has been taken to allow an easy implementation on different computer platforms. The present version can run on most of Unix stations (HP-Ux, Linux, IBM-Aix, Sun, ...) and on PC compatibles (80386 or higher) with MS-Windows95; previous releases were also run on Powermac and on Vax but compilation was not recently attempt on these hosts, care was not taken in the last release to ensure success with KK compiler as gcc is widely available.

The main features of this version are:

• (3+1) dimensional incommensurate displacive and substitutional modulated structures;
• (3+1) dimensional composite structures;
• multiple wavelenghts;
• X-ray, Synchrotron and neutron (constant wavelength) powder patterns;
• joint refinement of X-ray and Neutron powder data;
• pattern matching of diffracted intensities whithout a priori knowledge of the crystal structure.
• choice of the weighting scheme;
• spline or interpolation of background;
• no soft limit to the number of phases;
• preferred orientation functions defined in the reciprocal lattice;
• profile functions defined in the reciprocal lattice;
• analytical treatment of profile asymmetry for pseudo-Voigt;
• rigid body constraints;
• penalties on bond lenghts;
• boundaries on some variables are checked during minimisation .

References

• The first description of this program was presented at the I.U.Cr. Sat. Meeting, "Powder Diffractometry" kept in Toulouse in July 1990 (Bérar, 1990).
  
  
• A short description was given at the Advanced Powder Diffraction 2nd Conference organised by N.I.S.T.(U.S.) at Gaithersburg in May 1992 (Bérar, Garnier, 1992).
  
  
• The refinement of incommensurate modulated phases was presented at Aperiodic Conference in August97 (G. Baldinozzi, D. Grebille and J-F. Bérar, Proceedings of Aperiodic' 97, World Scientific (1999) p297-301), which contents can be seen as a postcript file.
  
  
• A description of the program can be found in the "Extended Software/Methods Development Issue" from the IUCr-CPD Newsletter #20 (1998) p3-5 or in a postcript file.
  
  

Credits

Source

However, on January 15th 2000, the CNRS ftp server is going to be changed and the xnd source can be obtained using anonymous-ftp from old-labs.polycnrs-gre.fr.

CCP14 mirror

Some tutorial is also in construction on this site. Thanks to Lachlan Cranswick for this works.

Author