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DPPA Settings

DPPA Settings

This section shows how the Settings panel is used to create settings files for use with the particular material and instrument being used in BIGdippa.

Back to Help Home DPPAdocs.html

The text in the grey boxes is code used to generate this html help file. Essentially what this code is doing is using command prompts to replicate the pressing of buttons on the GUI, and making some features of the GUI green to highlight them



In order to perform DPPA techniques it is first necessary to define:

  1. The crystallography of the material, so that the peak positions of different hkl reflections of different phases are defined
  2. The instrument. So that instrumental broadening can be removed and if the source is from a lab X-ray, the alpha 1 and alpha 2 components need to be defined.

The materials settings GUI

Pressing the 'New Material GUI' opens a seperate GUI that is used to define the phases in the material. In particular the position of the diffraction peaks and their hkl indices. If the materials settings have not previously been set this is a good place to start to define the material More details on this GUI is found here DPPA_NewMaterialGUI.html

gre =[0 0.8 0]; wht =[1 1 1];
% handles2=handles.startGo_b.Callback;

Add phases and peaks manually

Alternatively the phases of the material can be added on the left hand side of the Settings panel.

  • Change the name of the phase by changing 'phaneNom'.
  • Change the crystal structure by clicking the button marked 'Symmetry' to choose from FCC, BCC, HCP.
  • And enter the latice spacing(s) in the boxes below 'Lattice Spacing'

A peak can be added by entering the hkl index and pressing the '+' button. The list of peaks appears in the table on the left below 'Symmetry'. If no h k l index is entered into the index box, a peak can be entered from its position by clicking on the figure. This can be useful if there are additional peaks from other phases that you don't wish to analyse, but need accounting for to avoid overlap with other peaks


%give hkl index for 111 peak
handles.index_t.String ='1 1 1';
%give unit cell parameter of 2.9 Amstrongs
handles.lat1_t.String ='2.9';
%give FCC unit cell structure
handles.symm_l.String = 'FCC';

X-ray/ Neutron Instrument Settings

The instrument settings can be set on the mid-right of the Settings panel. There are 2 main settings available: * With an alpha-1 and alpha-2 components * With a single wavelength and no alpha or beta satellites For the former Cu and Co tubes are included as options. Additional tubes can be inserted into the scripts by modifying a few of the functions, mostly of 'pk_alpha.m'

The instrument settings are asked for when loading a sample, and so do not need to be set here


Instrumental Standard Settings

An instrumental sample is necessary to separate broadening due to the microstructure of the sample from broadening of the instrument. Hence to perform WA or WH analysis methods an instrumental sample measured from the same instrument as the other samples is required. If the GUI is only being used for fitting then an instrumental is not needed.

The instrumental sample can be changed from the buttons on the right hand side of the Settings panel. The way to introduce an instrumental sample:

  1. Load the instrumental data file using 'Load Standard' button
  2. Select the diffraction peaks of the sample using 'Select Peaks' button
  3. Fit the peaks of the standard by using 'Fit Standard' button This opens up the Fitting panel (DPPA_Fitting.html). Fit the peaks in this panel and press the 'Done' button to return to the Settings panel


Load and Save Setting

On the far right of the Settings panel are Save and Load buttons.

These are used to load and save 'Materials Settings' and 'Instrumental Standards'. The Instrument Settings are saved within these files.