Software for Crystallographic and Rietveld Analysis X’Pert Plus is an analytical software package for crystallographic and Rietveld analysis. It is applicable to all diffraction scans along the 2Theta-axis. Several types of basic actions are available in X’Pert Plus: Data treatment and corrections Data analysis (pattern assignment, crystallography and Rietveld) Auxiliary functions and tools This presentation gives an overview of the most important basic functions of X’Pert Plus.

Outstanding Features Easy to use Rietveld program Three indexing routines Unique tool to manipulate / simulate diffraction data Support of ASCII and binary data formats of all major suppliers X’Pert Plus is different from other software packages. For the first time it combines crystallographic analysis and Rietveld refinement into one tool with a common user interface. X’Pert Plus works on files, binary as well as ASCII formats are supported. It can be used to convert between file formats too. Structure data is read in *.CRY-format, specific to the ICSD organization or in *.CIF-format, as favored by the IUCr. Manual input of a certain structure is possible too. A conversion tool puts selected parts from the ICDD powder diffraction database PDF-2 on to the hard disk, which are then directly accessed by X’Pert Plus.

More Features... True 32-bit interface combines measurements, structural data and simulations Clipboard support for text and graphics, print preview and multiple Undo / Redo feature Auxiliary functions like Calculators, Periodic Table or Symmetry Explorer The new interface is true WINDOWS95 / WINDOWS NT and follows as much as possible the look and feel you are already used to (by for example the MS-Office suite). Many standard features like print preview, multiple undo / redo, clipboard support are available now. Formatted reports can be brushed up in MS-WORD or other text editors, tables are ready for import into MS-EXCEL or other spreadsheet calculators. A lot of auxiliary functions turn X’Pert Plus into a versatile toolbox, suitable for anybody involved in powder diffraction

X’Pert Plus Main Window Shown here is the main application window. It consists of three major parts: The main graphic window (upper left), which shows the anchor scan plus additional data (a calculated profile, peak sticks or pattern sticks, plus labels) The difference plot (lower left) shows either the difference between calculated and measured profile, or the distribution of peak full-width at half-maximum. The suite of tabs (right side), which displays numerical information The size of the three windows can be adjusted at will with the two splitter bars.

Data Treatment Smoothing Background Subtraction Peak Search Peak Fitting Systematic Error Correction Adjusting and Combining several measurements Data treatment is usually the first step before starting an analysis. It is used to extract the correct information from the measurements. Smoothing is done by either a sliding polynomial procedure or using a fast Fourier transform function. Background definition: either automatically, or by manually setting / moving base points or as a by-product from a previous peak search. Peak search: Peak hunting is done either the minimum of the second derivative or by the top of the smoothed peak method. Peak fitting: this is a manual profile fitting capable of dealing with some (<10) peaks at a time Systematic error correction uses an internal or external standard to correct your data for minor aberrations. Either the peak list or the complete scan (or both) are manipulated. Measurements can be added / subtracted as long as they have several data points in common. If necessary, the background or peak intensity as well as the 2Theta zero point are adjusted first.

Systematic Error Correction The systematic error correction dialogue shown here uses an internal standard. The difference between the actual measurement and the theoretical standard values is approximated by either a linear, a quadratic or a cubic function. This correction function is then used to correct the peak positions and / or the total scan. The right hand side of the screen shows one correction function (at the bottom) and the corresponding table of standard, measured and corrected values (at the top).

Crystallographic Analysis (1) Indexing DICVOL - all symmetries, especially monoclinic ITO - low symmetries up to orthorhombic TREOR - all symmetries, especially orthorhombic and higher Indexing - or finding a possible unit cell - is the first step in crystallographic analysis. High-quality data is an absolute must for a proper indexing. The first 6 - >20 reflexes are used. The three indexing routines have specific advantages and disadvantages. All possible results are presented in a common list, which is sorted (in the usual WINDOWS way - by clicking the column headers) at will. The original output of the indexing routines is available too. Indexing is started as a separate thread, because it could run for quite some time. If required, it can be aborted without leaving X’Pert Plus.

Search Unit Cell Dialogue Use the search unit cell dialogue to select an indexing algorithm. In addition you set important parameters to constrain the search. Attention: ALL results - no matter which algorithm was used - are written into the search results table. The original output of the indexing routines is available under the button “Show detailed Output”.

Crystallographic Analysis (2) Cell Refinement generation of theoretical reflections least squares refinement (including 2Theta zero or sample displacement) Systematic Extinctions Cell Reduction Cell Standardization Unit cell refinement is the second step in crystallographic analysis. Now ALL measured peaks are used. A least squares fit between the theoretical reflections and the observed peaks is carried out. A possible 2Theta zero shift or a known sample displacement can be taken into account. The observation of “systematic extinctions” further reduces the number of possible unit cells. Note: With a diffraction experiment alone it is impossible to determine the “one-and-only” correct unit cell! Cell reduction calculates the fully reduced cell and tries to find the conventional cell of highest possible symmetry. It is used to compare several monoclinic unit cells as well. Cell standardization is done by the well-known program “Structure Tidy”. Currently the Rietveld code accepts only standard unit cell settings!

Cell Refinement Dialogue This dialogue displays the results of the unit cell refinement at the right side. The left side is used to set some important parameters. The “advanced tab” contains more parameters and a list of possible space group candidates, when the button “Test Space Groups” has been activated.

Rietveld Analysis (1) True integrated Rietveld code, not just a user interface shell Range checking for each parameter Three different modes available: automatic (following a configurable script) semi-automatic (define the parameters for each step) manual (input valid codes yourself) X’Pert Plus has a true integrated Rietveld package, not just a user interface built around an existing executable. The benefits are: Range checking while the refinement is running You can follow the progress of the refinement at each step You can stop, undo, redo a Rietveld refinement or -in other words - total control through complete integration.

Rietveld Parameters The parameter turn-on dialogue consists of the general tab (shown here), and a tab for every structure. The general tab contains items valid for ALL structures in the application window, like the background parameters or the Rietveld mode. During and after a refinement the agreement indices are shown here, but the most important indices are displayed in the status bar as well.

Rietveld Analysis (2) Distances and Angles calculation (Difference) Fourier calculation Possibility to completely automate Rietveld analysis (command line interface) The calculation of distances and angles is a tool to check: a structure model the result of refining the atom positions a cell transformation (distances and angles before and after the transformation must be the same) Fourier calculation determines the electron densities in the unit cell. The densities are shown in “slices” along the Z-axis.

Fourier Map Shown here is a difference Fourier map. This is a representation of the difference in electron density between the crystal structure model and the measured intensities. It is used during structural analysis to find more atom positions not yet included in the model.

Rietveld Analysis (3) Rietveld analysis is used for: Simulation of powder diffractograms from a given structure Simulation of preferred orientation in eg. thin films Quantitative phase analysis Crystal structure refinement from powder diffraction data Rietveld analysis may be used for several purposes. (Please remember, that the crystal structure of every phase must either be known or - for strucure refinement - there must be a plausible model to start with!) Well known is the possibility to determine the weight percentages in a phase mixture. X’Pert Plus uses the Rietveld method to calculate a theoretical powder diffractogram from the structure information too.

Quantitative Result Shown is one possibility to report only the quantitative result of a multi-phase Rietveld analysis. The ordinary formatted results report contains the weight percentages as well, but doesn’t show the pie diagram. After a completely automated Rietveld run the quantitative result is available in form of an ASCII-file too.

There is much more to discover ! More of X’Pert Plus ... There is much more to discover ! Ask for a life demonstration - or try it out yourself ! X’Pert Plus is an analytical software package for crystallographic and Rietveld analysis. It is applicable to all diffraction scans along the 2Theta-axis. Several types of basic actions are available in X’Pert Plus: Data treatment and corrections Data analysis (pattern assignment, crystallography and Rietveld) Auxiliary functions and tools This presentation gives an overview of the most important basic functions of X’Pert Plus.