Relativistic four-component linear damped response TDDFT for electronic absorption and circular dichroism...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Relativistic effects are crucial for accurate molecular property calculations, especially for heavy elements.
• Time-dependent density functional theory (TDDFT) is a powerful tool for predicting molecular spectra.
• Previous methods had limitations in handling relativistic effects and complex spectral properties.

Purpose of the Study:

• To present a detailed theory and implementation of a relativistic four-component (4c) damped linear response TDDFT.
• To develop and present a robust multifrequency iterative subspace solver for damped response equations.
• To calculate and benchmark key spectroscopic properties like ECD and ORD using the new methodology.

Main Methods:

• Developed a 4c Dirac-Kohn-Sham formalism with restricted kinetic balance and a noncollinear exchange-correlation kernel.
• Employed a multifrequency iterative subspace solver, exploiting Hermitian and time-reversal symmetry for convergence.
• Calculated linear electric- and magnetic-dipole responses to predict frequency-dependent polarizabilities, absorption, ECD, and ORD spectra.

Main Results:

• Successfully implemented the methodology in the ReSpect program.
• Validated the approach on dimethylchalcogeniranes (C4H8X) and transition metal complexes ([M(phen)3]3+).
• Achieved the first reported 4c damped linear response TDDFT calculations for ECD and ORD spectra.

Conclusions:

• The new relativistic TDDFT method provides accurate predictions of molecular spectra, including ECD and ORD.
• The robust solver ensures reliable calculations for complex molecular systems.
• This work advances the capability for theoretical spectroscopy in relativistic quantum chemistry.