Powder diffraction simulation

While ReX main focus is the analysis of experimental powder diffraction data, it may also be used as a tool to simulate a powder diffraction pattern, given a sample model in the form of a mixture of crystallographic phases as well as a suitable instrument model. Starting from version 0.9.3, a powder diffraction simulation analysis can be setup by means of a guided wizard.

After starting ReX, the welcome screen is displayed by default; click the “New analysis wizard…” button to start the analysis wizard.

In the Wizard starting page select the “Powder diffraction simulation” radio button, then click “Next”.

The instrument setup page will be displayed; if no instrument is present in the project tree, as in our case, a default one will be created; you may also want to create a new one or loading a previously saved one, by clicking respectively the or button located on the left of the instrument combo.

After clicking Next >, the sample setup page will appear; if no sample is already present in the project, a default empty one will be created. Again, it is possible to manually create a new sample or load a preexisting one from a previously saved ReX project.

In our case, we will configure the newly created sample by loading crystallographic phases in the usual form of CIF files. To do so, just drag and drop in the composition table panel the Al2O3.cif and ZnO.cif files located in the cpd_qa folder of the examples archive, or a couple of other CIF files of your interest. When loading multiple files, make sure to check all the checkboxes of the phases you want to insert in your sample:

By default, each phase is defined with a 100% / n volume fraction, where n is the total number of phases. You may also change volume or weight fractions directly in the composition table or later in the analysis. Once done, click Next > ; the final setup page will appear:

Make sure to check the “Run analysis now ” checkbox and click the Finish button; the powder diffraction simulation will run and the simulated pattern will be displayed in the dataset plot window:

You may also want to restrict the default computation range to e.g. 20°-100°. To do so, click on the simulated Dataset object in the project tree and setup the desired 2theta range; after that, click the Run Analysis button to display the updated pattern, whose appearance can be configured as usual by clicking the Options button in the top right menu of the Dataset plot window.