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Pull request overview
This PR fixes a bug in the ORCA frequency parser where negative frequencies (imaginary modes) in transition states were incorrectly filtered out. The parser now correctly handles both positive and negative frequencies while still excluding exact zeros (translations/rotations).
Key changes:
- Modified the frequency filtering logic from
freq > 0toabs(freq) > 0.0to preserve negative frequencies - Added a test case with ORCA transition state output containing a negative frequency
- Included comprehensive test data file with a transition state calculation showing -1271.62 cm⁻¹ imaginary mode
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| arc/parser/adapters/orca.py | Fixed frequency filtering logic to preserve negative frequencies while excluding exact zeros |
| arc/parser/parser_test.py | Added test case for ORCA transition state with negative frequency |
| arc/testing/freq/orca_neg_freq_ts.out | New test data file containing ORCA TS calculation with imaginary mode at -1271.62 cm⁻¹ |
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kfir4444
approved these changes
Jan 11, 2026
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kfir4444
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kfir4444
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Amazing job! approved.
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ORCA, when used to parse for neg freq in a TS, would not pick up the negative freq. It would throw it away due to the line of code saying freq > 0.