Gauge-Invariant Formulation of Circular Dichroism

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Computational Physics

Background:

• Standard calculations of magnetic response properties, like circular dichroism (CD) spectra, suffer from gauge dependencies.
• These dependencies can lead to unphysical results, limiting the accuracy and reliability of theoretical predictions.

Purpose of the Study:

• To develop a general gauge-invariant and numerically efficient method for calculating CD spectra.
• To address the limitations of existing formulations by eliminating gauge dependencies.

Main Methods:

• Formulation of a gauge-invariant optical rotation tensor derived from current density.
• Demonstration of origin and gauge independence of the optical rotation tensor and its trace.
• Extension of the method for practical calculations using finite basis sets.
• Application to time-dependent current-density-functional theory (TD-CDFT).

Main Results:

• A novel gauge-invariant formulation for calculating CD spectra from current density.
• Demonstrated independence of the optical rotation tensor from coordinate system origin and gauge origin.
• Successful application of the method within the adiabatic local-density approximation (ALDA).

Conclusions:

• The developed method provides accurate and physically meaningful CD spectra.
• The gauge-invariant approach resolves critical issues in theoretical spectroscopy.
• The results show good agreement with experimental CD spectra, validating the new methodology.