Resolution-of-identity accelerated relativistic two- and four-component electron dynamics approach to chiroptical...

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Spectroscopy

Background:

• Accurate calculation of chiroptical spectra is crucial for understanding molecular properties.
• Relativistic effects become significant for heavier elements, necessitating advanced computational methods.

Purpose of the Study:

• To implement and apply electron dynamics using real-time time-dependent density functional theory (RT-TDDFT) with relativistic Hamiltonians.
• To introduce and integrate the resolution-of-identity approximation for the Coulomb term (RI-J) into RT-TDDFT.
• To assess the performance and accuracy of the developed methodology for calculating electron circular dichroism and optical rotatory dispersion spectra.

Main Methods:

• Utilized real-time time-dependent density functional theory (RT-TDDFT).
• Employed relativistic 2-component X2C and 4-component Dirac-Coulomb (4c) Hamiltonians.
• Integrated the resolution-of-identity approximation for the Coulomb term (RI-J) using complex quaternion algebra.
• Applied the methodology to the dimethylchalcogenirane series (C4H8X, X = O, S, Se, Te, Po, Lv).

Main Results:

• Spectra calculated by non-relativistic and relativistic methods showed increasing disagreement for heavier elements (Se, Te, Po, Lv).
• The X2C approach accurately reproduced 4c results with an 8-fold speed-up.
• Combined X2C and RI-J acceleration achieved a speed-up factor of almost 25 compared to full 4c treatment, maintaining spectral accuracy.

Conclusions:

• One-particle X2C electron dynamics with RI-J acceleration is a highly efficient and accurate method for calculating chiroptical spectra.
• This approach is particularly attractive for studying molecules containing heavier elements where relativistic effects are pronounced.
• The developed methodology offers a significant advancement for computational spectroscopy in the valence region.