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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.

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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:

• 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.
  
  Image AddedFigure 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.

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• Databases : includes DB Filter and Chemical
• Match Lists
• Names
• Options

Select the desired search parameters (see suggestions below and Figures 6, 7 and 8).

Image AddedFigure 4. A. Search/Match, B. Auto Views Panel, C. Search/Match dialog box

In the Criterion field of the Options Tab (Figure 5), begin the search with 2: Neutral.

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Figure 5. Options Tab of Search/Match dialog box.

Database Filter

In the Databases Tab, select the DB Filter. Click on the "three dots" button (Figure 6A). The Database Filter window opens (Figure 6). 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 6):
–Quality Marks: Degrees of pattern quality assigned by ICDD. Recommended: *, Calculated, Indexed (a).
–Status: Recommended: Primary (b).
–Colors: Select the color of the mineral to be searched.
–Sources: Database section: select both ICDD Database (experimental) and ICSD Database (ICSD-FIZ) (c).
–Subfiles: Select the group of patterns to be searched, for example, inorganics, zeolites, minerals, etc. (d).
–Element # in Formula: Choose the minimum/maximum number of elements considered in the formula (default values are min=1 and max=24).
–Density: Enter a minimum/maximum density for the mineral being searched (default values are min=1 and max=80).

Image AddedFigure 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.

Image AddedFigure 7. Chemical Filter.

Once the desired parameters are selected, click Rebuild to rebuild the database for your selections (Figure 6B). After the database is rebuilt, click back onto Match Lists (Figure 8). In the drop-down menu, select the list of clay minerals and common minerals and click OK (Figure 8A). Then, click Match (Figure 8B).

Close the window.

Image AddedFigure 8. Match Lists

In the Auto Views panel, the list of candidates appears (Figure 9). Expand the table to see important information on the candidate (Figure 9), including:

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Check the tick box (green square in Figure 8) to add selected peaks. To delete selected peaks, right-click on the selection and choose 'Delete'.

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Figure 8. Search List Tab in the Auto Views Panel

Residual Scan – Searching the minor phases

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Check the tick box (green square in Figure 9) to add selected peaks. To delete selected peaks, right-click on the selection and choose 'Delete'.

Image AddedFigure 9. Residual Scan

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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The Peak Search with the Appended list appears in the Data Tree Panel (Figure 12).

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Figure 10. Peak Search.

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Figure 11. Making Peaks

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Figure 12. Peak Search with Append List.

Printing in EVA

You can print any of the views in EVA.
Click Print Preview Button or click File > Print Preview. A 'Print Preview' window pops up. This allows you to enter header and footers onto your print out, in addition to editing axis and labels. You can then click on Export as Image Button and save the print preview as an image .PNG file.

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