| # | 2θ Obs (°) | d (Å) | Del |
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| Sys. | Parameters (Å) | Angles (°) | Vol | M(20) |
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This program uses a system-specific, exhaustive search to find potential unit cells based on the first 20 peaks. For Ortho, Monoclinic and Triclinic searches, a GPU is required and activate in the browser.
All trial cells are refined, scored (M(20)), and analyzed for space groups. For a full breakdown, read the technical guide.
Generic 2-column (2θ intensity), .xrdml, .xml, .ras, .uxd, .udf, GSAS .esd. Data, either raw or K& stripped, can be saved in various formats.
Zoom: Use the mouse wheel, or select an area. Right-click to reset zoom.
Pan: Alt + drag the chart to pan.
Add Peak: Hold Ctrl and click on the chart to manually add a peak at that position.
Load a data file to begin indexing.
Monte-Carlo search around the selected cell, constrained to its crystal system. Zero is refined as an extra parameter when "Refine Zero" is on. The result is added as a new solution only if it improves M20.
Every space group of this crystal system is tried as a hypothesis: its forbidden reflections are removed from the calculated line list, the cell is re-refined against what is left, and the evidence is recomputed. Rule sets that produce the same calculated pattern for this cell, wavelength, range and tolerance cannot be separated by the data, so they share one row and are labelled by extinction symbol rather than by a representative group. Ranking is in two tiers. A row with a hard violation the impurity allowance does not cover is falsified - a single genuine reflection on a forbidden line rules a group out - and can never outrank a row with none, whatever its score. Falsified rows are shown below, ordered least-bad first. Score is the log-odds in nats against the leading row of its own tier: it rewards forbidden lines that are cleanly empty (Clean) and penalises observed peaks that only a forbidden line explains (Viol, hard count with soft Ka2/weak/ambiguous ones in brackets) and peaks the refined cell cannot explain at all (Unidx). Rows within about 2.3 nats of each other are a tie. M20 describes the refined cell only - it rises whenever lines are deleted, so it is not what ranks the hypotheses, so the table is sorted by Score by default. Click any header to sort by that column instead, and click it again to reverse. The row leading on Score stays bold wherever the sort puts it. Select a row to keep its refined cell.
| Class | Space groups | Lines | M20 | Score | Clean | Viol | Unidx | Zero |
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Edit any assignment, then Apply to create a new refined solution. Blank rows are left unchanged.
| 2θ obs | d obs | h | k | l | 2θ calc | diff |
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