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One-electron contributions to the g-tensor for second-order Douglas-Kroll-Hess theory
1Max Planck Institute for Bioinorganic Chemistry, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
The Journal of Chemical Physics
|September 11, 2012
Summary
This study details electron paramagnetic resonance g-tensor calculations using relativistic quantum chemistry. It clarifies the Douglas-Kroll-Hess transformation in magnetic fields, crucial for accurate spectral interpretation.
Area of Science:
- Quantum Chemistry
- Spectroscopy
- Relativistic Effects
Background:
- The electric g-tensor is vital for interpreting electron paramagnetic resonance (EPR) spectra.
- Accurate theoretical calculations of the g-tensor require relativistic quantum chemical methods.
- The Douglas-Kroll-Hess (DKH) transformation is a key relativistic method, but its application in magnetic fields presents ambiguities.
Purpose of the Study:
- To provide a detailed derivation of 1-electron contributions to the g-tensor within linear response theory and DKH transformation.
- To compare different Foldy-Wouthuysen transformation approaches within the DKH framework in the presence of magnetic fields.
- To physically interpret the resulting Hamiltonians and compare them with conventional Pauli theory.
Main Methods:
- Linear response theory
- Second-order Douglas-Kroll-Hess (DKH) transformation
- Density Functional Theory (DFT) calculations
- Comparison of gauge-invariant vs. non-gauge-invariant Foldy-Wouthuysen transformations
Main Results:
- Established the necessity of a gauge-invariant Foldy-Wouthuysen transformation (including the magnetic field) for the DKH approach with constant magnetic fields.
- Quantified picture-change effects in relativistic g-tensor calculations for heavy diatomic molecules, transition-metal complexes, and Lanthanide dihydrides.
- Elucidated periodic trends in g-tensor calculations, highlighting the impact of relativistic effects.
Conclusions:
- The gauge-invariant Foldy-Wouthuysen transformation is the correct approach for relativistic g-tensor calculations in magnetic fields.
- Picture-change effects are significant and vary systematically across the periodic table.
- The developed methodology provides accurate g-tensor predictions, essential for EPR spectral interpretation.
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