Federal Institute for Materials Research and Testing

PowderCell 2.3 —  powder pattern calculation from single crystal data and refinement of experimental curves

General

Fig.1: 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.

Fig.2: 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.

Basic properties

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 symmetry density,
• 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).

PowderCell 2.3 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 orientation...
• 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 powder data (LeBail algorithm)