OpXRD troubleshooting

This page helps you diagnose why an OpXRD search or similarity match returns no results or low scores, and why pattern data fails validation — usually a filter or data-format mismatch rather than a missing phase.

OpXRD troubleshooting

No patterns found for element search

Symptom: search_patterns returns zero results.

Causes and fixes:

• Rare element combination: The database may not contain patterns for unusual compositions. Try broader filters (single element instead of a combination).
• elements_exclusive too strict: Switch it from true to false to include compounds with additional elements beyond the ones listed.
• Misspelled element symbol: Element symbols are case-sensitive (Fe not fe or FE).
• Wrong spacegroup filter: spacegroup takes the space group number (1-230), not a Hermann-Mauguin symbol — "Fm-3m" won't match anything. If you only know the symbol, look up its number or filter by chemical_formula/elements instead.

Similarity search returns low scores

Symptom: All matches have similarity below the threshold.

Causes and fixes:

• Wavelength mismatch: similarity_search has no wavelength parameter — it compares raw 2-theta positions. If your experimental data was collected with Mo K-alpha (0.7093 Å) rather than Cu K-alpha (~1.5406 Å), your peaks sit at different 2-theta angles than the database's Cu-K-alpha-indexed patterns and the fingerprint will not match. Convert your pattern to d-spacing or an equivalent Cu-K-alpha 2-theta scale before submitting two_theta_values.
• Background not subtracted: High background noise dilutes the fingerprint signal. Subtract the background before running similarity search, or use PyWPEM background fitting first.
• Amorphous sample: Amorphous materials produce broad humps rather than sharp peaks. The database primarily contains crystalline patterns.
• Low threshold: Try lowering similarity_threshold to 0.5 to see if any weak matches emerge, and try similarity_metric: "pearson" or "euclidean" if cosine scores poorly.

Pattern data validation failed

Symptom: A "Similarity search requires both two_theta_values and intensities arrays" or pattern-validation error.

Fixes:

• Provide both two_theta_values and intensities as separate, same-length arrays — there is no combined pattern_data field
• Two-theta values must be positive
• Intensity values must be non-negative

Job timed out

Symptom: Job exceeds the default timeout.

Causes:

• Similarity search against the full database with a very low threshold can be slow
• Increase the threshold or reduce max_results
• If timeouts persist, the Modal volume may be temporarily unavailable. Retry after a few minutes.

Fingerprint computation fails or returns null

Symptom: compute_fingerprint returns an error or a null fingerprint.

Fixes:

• compute_fingerprint takes a crystal structure (cif_content or structure_dict), not a raw diffraction pattern — it is a different input shape from similarity_search. Passing two_theta_values/intensities here will not work.
• Verify the CIF content parses as a valid structure; malformed or incomplete CIF files return "Failed to compute fingerprint".
• If you only have an experimental pattern (no structure), use similarity_search instead, which compares patterns directly rather than computing a structure-derived fingerprint.

Getting help

If issues persist:

1. Check the job logs in the .bloom* job panel for specific error messages
2. Verify your input format against the examples in the inputs page
3. Describe the issue to Ivy

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