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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Figure 2. View of a Diffractogram in EVA
Removing the Background
The first step in preparing a scan for Search/Match phase identification is to subtract the background (Figure 3). There are two methods for removing the background:
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In Data Command Panel, select Tools > Background to open the Background dialog box (Figure 3). Default view is 'Original + Background'. If needed, use the slider on the left to adjust the curvature on background humps. When satisfied, in the drop-down box, select Background subtracted option. Close the text box 
. The background is removed, and the diffractogram is changed to baseline.
Search/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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| 1. | Select Search/Match (scan) from Data Command Panel > Tools. Notice the Search/Match dialog box has four tabs (Figure 5): –Chemical Filter –Database Filter –Candidate List –Selected Candidates | |
2. | Select desired search parameters (see suggestions below; Figures 6, 7, 8). | |
3. | Once the desired parameters are selected, click Rebuild to rebuild the database for your selections. After the database is rebuilt, click back onto Candidate List and click Match. |
Search/Match Screen
In the Criterion field of the Candidate List Tab (Figure 5), begin the search with 2: Neutral.
Figure 5. Search/Match Screen.
Chemical Filter Tab
A chemical filter can be set for any element in the periodic table (Figure 6).
–Green = element is mandatory
–Red = must be absent
–Blue = at least one of the elements in blue must be present in the search result
–Gray = not checked (absent or present) 
Figure 6. Chemical Filter Tab.
Database Filter Tab
Search/Match can be enhanced using database filters such as the following (Figure 7):
–Quality Marks: degrees of pattern quality assigned by ICDD (recommended: *, Calculated, Indexed).
–Status: recommended: Primary.
–Colors: select the color of the mineral to be searched.
–Sources: database section: select both.
–Subfiles: select the group of patterns to be searched, for example, inorganics, zeolites, minerals, etc.
–Element # in Formula: choose the minimum/maximum number of elements considered in the formula.
–Density: enter a minimum/maximum density for the mineral being searched.
Figure 7. Database Filter Tab.
Candidate List Tab
Expand the table to see important information on the candidate (Figure 8), including
–Mtc: number of reference pattern lines matching the unknown
–FOM: Figure of Merit – a lower number is a better match
–Index #: rank number of the pattern
Figure 8. Candidate List Tab.
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. |
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.
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.
Credits
This document originated from Word document XRD_EVA_QSGV1.2_368X.doc (see Archived Versions below for a pdf copy) that was written by H. Barnes and K. Bronk; later edited by N. Lawler and A. Armstrong. Credits for subsequent changes to this document are given in the page history.
Archived Versions
LMUG-XRDDiffrac.EVAQuickStartGuide-111221-1202-232.pdf
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