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XRD DIFFRAC.EVA:
Quick Start Guide
V371T | July 2017/ Reviewed X374/ March 2018
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This guide is a quick introduction to the DIFFRAC.EVA software 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 XRD lab or online in Cumulus.
Part 1: Opening Diffractogram in DIFFRAC.EVA
To open a diffractogram for evaluation:
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The DIFFRAC.EVA main screen has the following primary functional areas (Figure 2):
1. | Toolbar |
2. | Data Command Panel |
3. | View Command Panel |
4. | View Window |
5. | Data/View Tree Panel |
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Figure 4. Background Dialog Box.
Part 3: Search Match
The Search Match tool 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 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.
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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.
Part 4: Residual Scan – searching the minor phases
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Peak Search detects peaks automatically and is useful for phases not identified with Search/Match or to export the pattern to another program.
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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