Table of Contents
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Introduction
This guide is a quick introduction to the DIFFRAC.EVA software (version 5.1) and how to use the program to solve crystalline phase identification. For detailed information and an in-depth guide refer to DIFFRAC.EVALUATION User Guide & Tutorial available in hard copy in the X-Ray Lab or online in Cumulus at XRD Books and Reference Material.
Opening a Diffractogram in DIFFRAC.EVA
To open a diffractogram for evaluation:
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1.
Click File > Import
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from Files (Figure 1)
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.
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Select the
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scan you want to open.
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3.
It is usually in C:\DIFFDAT1\D4 Bruker. Click Open.
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4.
The
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scan is now open and ready for evaluation.
Figure 1. Open Scan.
Getting Acquainted
The DIFFRAC.EVA main screen has the following primary functional areas area (Figure 2):
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1.
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Toolbar
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2.
a Toolbar, a Data Command Panel
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3.
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View Command Panel
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4.
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View Window
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5.
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Data/View Tree Panel
, a View Window, a Data Tree Panel, and a Data Property Panel. An additional window, called 'Automatic Views Panel' can be open by clicking View > Automatic Views Panel in the top menu.
It is useful to have the Data Command Panel and Data Tree Panel open for view at all times
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. Use the icons in the
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Toolbar to open/close these views
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. 
Figure 2. View of a Diffractogram in EVA
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Removing the Background
The first step in preparing a scan for
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Search/
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Match phase identification is to subtract the background (Figure 3). There are two methods for removing the background:
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- Traditional method: is recommended for all scans; it gives an arc parabola but never submerges a complete peak.
- Enhanced method: gives a smooth curve where some peaks may be under the background curve. This could be useful for crystallographic studies. See the EVA manual for greater detail.
Figure 3. Background Highlighted in a Diffractogram
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1.
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and Background Dialog Box in inset
In Data Command Panel
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, select Tools > Background to open the Background dialog box (Figure
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3).
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2.
Default view is 'Original + Background'. If needed, use the slider on the left to adjust the curvature on background humps.
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3.
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When satisfied, in the drop-down box, select Background subtracted option
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.
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Close the text box
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. The background is removed, and the diffractogram is changed to baseline.
Search/
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Match
The Search/Match (scan) tool in the Data Command Panel attempts to match XRD scans with patterns found in the ICDD (International Centre for Diffraction Data) PDF database. The Search/Match process tries to identify an unknown scan based on pattern recognition techniques. EVA can also find a reference pattern by its name or ICDD number.
Note: It is at the user's discretion to identify and choose the correct pattern matches.
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Figure 8. Candidate List Tab.
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Residual Scan – searching the minor phases
Minor phases are often difficult to identify because the patterns of the major peaks are higher on the list. Using the Residue tool will exclude the already matched patterns and increase the weight of the minor phases.
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1. | Select the Scissors tool from the View Window toolbar. |
2. | Cut the peaks that you wish to exclude from the Search/Match. |
3. | Under Search/Match (scan) box,in the Candidate List tab, select Match. |
4. | The program will search the peaks left uncut. |
5. | To undo the cuts click the Undo Arrow. |
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Peak Search
Peak Search detects peaks automatically and is useful for phases not identified with Search/Match or to export the pattern to another program.
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Figure 10. Peak Search with Append List.
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Printing in EVA
You can print any of the views in EVA.
Print Preview allows you to enter header and footers onto your print out, in addition to editing axis and labels. You can also Export the print preview as an image *.PNG file.
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