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Component-wise AO basis reduction: norm loss, negative contribution normalization, and functional implications
1Institute of Chemical Physics, Vilnius University, Saulėtekio av. 3, Vilnius, LT-10257, Lithuania. mindaugas.macernis@ff.vu.lt.
Physical Chemistry Chemical Physics : PCCP
|June 26, 2025
Summary
Atomic orbital (AO) normalization is crucial in electronic structure theory. Inconsistent AO normalization impacts calculations, affecting Raman intensities and coupling constants, vital for spectroscopy and quantum computing.
Area of Science:
- Computational chemistry
- Quantum mechanics
- Spectroscopy
Background:
- Atomic orbital (AO) normalization is fundamental in electronic structure theory.
- Quantum chemistry packages may alter AO norms during calculations.
- Basis function reduction and transformations can lead to norm deviations.
Purpose of the Study:
- To develop a framework for analyzing AO normalization consequences.
- To quantify norm loss and its contributions (constructive/destructive).
- To enable precise renormalization of AO representations.
Main Methods:
- Implemented a systematic methodology to analyze AO normalization.
- Quantified norm loss and separated contributions.
- Evaluated sensitivity using a carotenoid (lycopene) and a phosphorus dimer.
Main Results:
- Vibrational frequencies were stable across normalization schemes.
- Raman intensities shifted by over 50 units.
- J-coupling constants for phosphorus shifted by up to 6 Hz.
Conclusions:
- AO normalization is a physically significant step, not just numerical.
- Deviations impact precision spectroscopy and quantum computing.
- Precise renormalization is necessary for accurate results.
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