2.3 powder pattern calculation from single crystal data and refinement of experimental curves
General The aim of PowderCell is at first an
intuitive structure modification by manipulation step by step and an
quasi-simultaneous comparison between experimental data and calculated powder
diffraction pattern. At second the program contains refinement procedures to
adapt experimental and theoretical data automatically. From our point
of view it is recommended to have an user-friendly shell, which is focused on
the only necessary input data or the solution of powder diffraction
problems exclusively. However, this is not a disadvantage particularly a lot of
interesting information the user is able to extract, e.g. concerning crystal
symmetry or phase composition, grain size, strain etc.
||The screenshot shows the outfit of the program. Please notice that you are able to work with more than one structure simultaneously.
The given model represents the structure of quartz and has been created using POVRay.
||Interaction between a structure manipulation (torsion of a molecule fragment) and the resulting powder pattern. For the sake of simplicity only one molecule has been shown. The sequence has been created using POVRay.
With the help of PowderCell you are e.g. able to
- use different import formats for structure data (ICSD, SHELX, POWDER CELL),
- display crystal structures using more than 740 different settings of space-group types,
- transform the different settings for monoclinic, orthorhombic and rhombohedral space-group types into another,
- generate all klassengleiche and translationengleiche subgroups an excellent tool for the investigation of phase transitions or other effects described by an decrease of
- vary the structure arrangement within the unit cell using rotation and translation of atoms or molecules selected before,
- display the corresponding X-ray or neutron powder diffraction patterns simultaneously for up to 10 phases,
- simulate different diffraction conditions, e.g. radiation, doublet splitting, diffraction geometry, variable slits, preferred orientation, anomaleous dispersion, any volume or mass fractions in a phase mixture etc.
- select different convolution functions,
- compare experimental and calculated diffractograms graphically and/or using R-values,
- export the crystal structure and the simulated powder pattern in different graphic formats (e.g. Windows Metafile, PostScript, POVRay),
- use the clipboard to paste graphics and reflection tables into other Windows programs,
- export the diffraction patterns in different file
formats (e.g. Siemens Diffrac AT: *.raw).
offers interesting new features, e.g.
- extended overview of all generated atomic positions, bonding angles and
distances, space-group information (general and special positions, Wyckoff
notation, list of all maximal subgroups incl. transformation of unit cell axis
and origin shift)
- automatical refinement of experimental and simulated powder diffraction data
using background polynom, scaling factors, variation of lattice constants,
zero shift, reflection broadening, convolution function, preferred
- calculation of size and strain
- excluded regions in experimental diffraction patterns
- quantitative phase analysis
- decomposition of reflections for an estimation of
structure amplitude regarding structure analysis from
PowderCell is an excellent tool to
- support the structure determination using powder diffraction data
- facilitate the teaching because of the simulation of
experimental influences on powder pattern or the visualisation crystallographic properties (space-group symmetry, special positions, extinction laws, subgroups....)
- support practical problems, e.g. quantitative
analysis of mixtures, phase identification, existence of preferred
orientations, estimation of grain size and lattice strain etc.
||For a more detailed description, please click
Notes on the download
The programs have been compressed as zip (DOS) or selfextracting file
(version 2.3). There is no installation procedure! Also no
DLL'S will be copied in other directories.
|We ask all users of the program to
send us an e-mail. This
give us the posibillity to demonstrate the benefite for the public. Only
on this way the program can be developed also in future!
||Pentium, Windows 9x or NT;
8 MByte RAM; appr. 5 MByte on hard disk (however: The
faster the better! )
Feel free to contact us:
- Federal Institute for Materials Research and Testing (BAM)
- Unter den Eichen 87,
- > D-12205 Berlin
You are the
at latest actualized: 10.02.2000
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