feat: add orbital mapping constants for ABACUS, DeePTB, and OPENMX

[QG-phy]

Add orbital number mappings and transformation matrices for ABACUS, DeePTB, and OPENMX DFT codes. These constants define the magnetic quantum number ordering and provide conversion matrices between different code conventions, enabling proper orbital basis transformations.

Summary by CodeRabbit

• New Features
  • Enhanced support for OpenMX computational package with new orbital number mappings.
  • Improved orbital data handling across ABACUS, DeePTB, and OpenMX packages.
  • Expanded configuration support for accurate data conversion between different computational software formats.

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📝 Walkthrough

Walkthrough

Added new orbital number mappings for ABACUS, DeePTB, and OpenMX platforms defining per-angular-momentum lists. Introduced new OpenMX2DFTIO mapping with 2D-FFT index-to-identity configuration. Expanded ABACUS2DFTIO public mapping with updated index configurations across multiple orbital blocks.

Changes

Cohort / File(s)	Summary
Orbital and format mappings dftio/constants.py	Added three new orbital number mappings (ABACUS_orbital_number_m, DeePTB_orbital_number_m, OPENMX_orbital_number_m), introduced OPENMX2DFTIO with 2D-FFT index-to-identity mapping, and expanded ABACUS2DFTIO with updated index configurations across multiple orbital blocks.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

• Verify correctness and completeness of the three new orbital number mappings for different angular momentum values
• Validate the OPENMX2DFTIO 2D-FFT index-to-identity mapping aligns with OpenMX format specifications
• Confirm updated index configurations in expanded ABACUS2DFTIO mapping are correct across all affected orbital blocks

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly and specifically describes the main change: adding orbital mapping constants for three DFT codes (ABACUS, DeePTB, OPENMX).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 75c66b5 and fb1d7c9.

📒 Files selected for processing (1)

• dftio/constants.py (2 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.py

📄 CodeRabbit inference engine (GEMINI.md)

Follow PEP 8 conventions for coding style in Python files

Files:

• dftio/constants.py

🔇 Additional comments (4)

dftio/constants.py (4)

15-22: LGTM!

The magnetic quantum number ordering follows a consistent pattern [0, 1, -1, 2, -2, ...] and element counts match expected values for each angular momentum (2l+1).

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24-31: LGTM!

Standard ascending magnetic quantum number ordering [-l, ..., 0, ..., l] is correctly defined for each angular momentum.

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80-85: Verify: OPENMX orbital support limited to f orbitals.

OPENMX_orbital_number_m only defines orbitals up to "f" (l=3), while ABACUS_orbital_number_m and DeePTB_orbital_number_m extend to "h" (l=5). If OPENMX supports g and h orbitals, consider adding those entries for consistency.

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87-92: OPENMX2DFTIO appears incomplete and unused; clarify design intent.

This transformation matrix is not imported anywhere in the codebase and lacks an OPENMX parser implementation. Additionally, it:

• Defines only l=0 to l=3, while ABACUS2DFTIO, RESCU2DFTIO, and SIESTA2DFTIO all extend to l=5
• Omits the sign-flipping adjustments applied by all three other matrices

Clarify whether this is intentional stub code pending OPENMX parser implementation or should be removed as dead code. If completion is planned, verify whether sign modifications are needed to match other codes' phase conventions.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.40%. Comparing base (317869d) to head (fb1d7c9).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #25      +/-   ##
==========================================
+ Coverage   40.35%   40.40%   +0.04%     
==========================================
  Files          43       43              
  Lines        4864     4868       +4     
==========================================
+ Hits         1963     1967       +4     
  Misses       2901     2901              

Flag	Coverage Δ
unittests	40.40% <100.00%> (+0.04%)	⬆️

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