Match! Basics

Match! is a program for phase analysis using powder diffraction data. By comparing the diffraction pattern of an unknown sample to patterns of known compounds stored in a database, it is able to identify the phases present in the unknown sample (or at least helps the user to do so...). The layout of the working area in the main window of Match! has been designed to best suite the requirements of this task.

Generally, a qualitative analyis (identification of the phases present in an unknown sample/powder) proceeds as follows:

• The X-ray diffraction pattern of the unknown sample is measured with highest possible accuracy and signal/noise ratio. The result is nowadays a file containing intensity vs. 2theta data (the so-called "raw data"), sometimes also experimental conditions.
• This diffraction data file is imported into the search-match software.
• As the diffraction data generally are raw (profile) data, the so-called "raw data processing" has to be carried out. This includes
  • stripping of the alpha-2-radiation (if present),
  • data smoothing,
  • background subtraction,
  • peak searching,
  • profile fitting, and
  • correction for errors.
  The goal is to obtain a list of peaks (2theta and intensity values) with highest possible precision. It is extremely important that this step is performed as accurate as possible in order to obtain reasonable results in the search-match process later on!
• If additional information is available about your sample (like chemical class, composition, density, color etc.), you should use it as restraints for the search-match calculation.
• Once the list of peaks is available, the actual search-match process can be performed: The software compares each diffraction pattern in the reference pattern database to the pattern of the unknown sample. It calculates a numerical value indicating the degree of the agreement, the so-called "figure-of-merit" (FoM).
• When the search-match has been finished, the entries are ranked according to their FoM values. The entries with the highest FoM are the ones which are most likely to be present in the sample. The ranked list of entries is then presented to the user.
• The user analyzes the entries at the top of the candidate list and selects those which are most likely to be present in the sample ("matching entries/phases").
• Once the matching phases have been selected, there should be a Rietveld refinement of these phases against the original raw (profile) data. A successful refinement is generally taken as the proof that the phase analysis is correct and complete.
• Finally, the user reads and/or prints the report in order to document the result of the phase analysis.

Remarks:

• Match! provides an undo/redo facility. You can undo nearly any operation until you return the new empty Match! document where you started. On the other hand, you can also return to the state before you executed the "undo" command(s) using "redo". You should use these options extensively in order to try different options !
• In addition to the menus, context menus and the toolbar buttons, you can also use a variety of keyboard shortcuts to perform the most common operations. Once you know these shortcuts by heart, your work will become much faster and more efficient.
• If you like, you can add the following citation/reference for Match! in your paper:
  
  Match! - Phase Analysis using Powder Diffraction, Crystal Impact - Dr. H. Putz & Dr. K. Brandenburg GbR, Kreuzherrenstr. 102, 53227 Bonn, Germany, http://www.crystalimpact.com/match