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
The program
Users Files
Usage and related info
Installation and structure of the program
- Installation guide.
- Structure of the program.
The program XND is devoted to the refinement of crystal structures
starting from powder diffraction patterns. The structure refinement is
carried out through the Rietveld (1969) method. The aim of the program is to
provide an easy approach to the treatment of multiple diffraction patterns
arising from a large number of physical and chemical problems
as the study of phase transition and in the real time monitoring of reactions.
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 .
- 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.
Numerous people have been concerned by previous releases and have
participated to the debugging. Friends of my previous laboratory
(CPS-ECP, Chatenay, France) have to be thank for their help in
finding lots of things ... and for their suggestions ...
The incommensurate modulation were introduced for them;
D. Grebille (CRISMAT, Caen, France) and
G. Baldinnozzi (CPS-ECP) have corrected the calculation of the
satelites. GB is also responsable for improvments in
the documentation being at the origin of this document.
The program files can be obtained using ftp anonymous on ftp.polycnrs-gre.fr
or labs.polycnrs-gre.fr, they are located in the pub/xnd directory.
It contains the current sources in the classical .tar.gz archive and some binaries,
as in this example.
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.
At the time, the program files
and the documentation are mirrored by
CCP14. There are also
Canadian and
USA XND mirrors
from the CCP14.
Some
tutorial is also in construction on this site. Thanks to Lachlan Cranswick for this works.
J.-François Bérar
Laboratoire de Cristallographie - CNRS,
BP 166, 38042 Grenoble CEDEX 09, France
e-mail: berar@polycnrs-gre.fr
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