Table of Contents
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To open a diffractogram for evaluation:
Click File > Import from Files (Figure 1). Select the scan you want to open. It is usually in C:\DIFFDAT1\D4 Bruker. Click Open. The scan is now open and ready for evaluation.
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Figure 1. Open Scan.
The DIFFRAC.EVA main screen has the following primary functional area (Figure 2): a Toolbar, a Data Command 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. Use the icons in the Toolbar to open/close these views. 
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:
- 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 and Background Dialog Box in inset
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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In Data Command Panel > Tool, select Search/Match (scan)
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(Figure 4A). 'Auto Views Panel' pops up if not open yet (Figure 4B). Notice the Search/Match dialog box has four tabs (Figure
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4C):
–Chemical Filter
–Database Filter
–Candidate List
–Selected Candidates
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2.
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- Databases : includes DB Filter and Chemical
- Match Lists
- Names
- Options
Select the desired search parameters (see suggestions below
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and Figures 6, 7
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and 8).
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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.
Figure 4. A. Search/Match, B. Auto Views Panel, C. Search/Match
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dialog box
In the Criterion field of the Candidate List Options Tab (Figure 5), begin the search with 2: Neutral.
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Figure 5. Options Tab of Search/Match Screendialog box.
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Database Filter
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In the Databases Tab, select the DB Filter. Click on the "three dots" button 
. The Database Filter window opens (Figure 6).
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Figure 6. Chemical Filter Tab.
Database Filter Tab
The default name is 'Database Filter #1', and the database used is "PDF-2 2001". The Search/Match can be enhanced using database filters such as the following (Figure
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6):
–Quality Marks:
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Degrees of pattern quality assigned by ICDD
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. Recommended: *, Calculated, Indexed (a).
–Status:
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Recommended: Primary (b).
–Colors:
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Select the color of the mineral to be searched.
–Sources:
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Database section: select both ICDD Database (experimental) and ICSD Database (ICSD-FIZ) (c).
–Subfiles:
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Select the group of patterns to be searched, for example, inorganics, zeolites, minerals, etc. (d).
–Element # in Formula:
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Choose the minimum/maximum number of elements considered in the formula (default values are min=1 and max=24).
–Density:
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Enter a minimum/maximum density for the mineral being searched
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(default values are min=1 and max=80).
Figure 6. Database Filter.
Chemical Filter
In the Databases Tab, select Chemical. Click on the "three dots" button . The Chemical Filter window opens (Figure 7). The default name is 'Chemical Filter #1'. A chemical filter can be set for any element in the periodic table (Figure 7).
–Green = M = Mandatory. All elements shall match.
–Red = D = Discarded. Exclude from match.
–Blue = A = At least one element shall match (must be present in the search result).
–Gray = N = Neutral. Element may match.
To select an element, click on the element to change its status (e.g., M, D...) as desired.
Figure 7. Database Chemical 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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1. | Select the scan in the data tree. |
2. | Click Peak Search in the Tool List of the Data Command Panel. The Peak Search dialog box is displayed. |
3. | Move the slider to select the peaks you desire (Figure 9). |
4. | Once you are satisfied, click Make Dif to create a DIF pattern. The pattern list is created in the Data Tree and can be Search/Matched. |
5. | To select specific peaks click Append to List and a peak list is created in the Data Tree (Figure 10). |
6. | Highlight the peaks you want and click Search/Match (peak list) under Tool or Make DIF Pattern (which you can export 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.
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