Density functional calculations of molecular parity-violating effects within the zeroth-order regular approximation

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Parity-violating effects in chiral molecules are of significant interest for experimental measurement.
• Accurate computation of these effects requires sophisticated relativistic quantum chemical methods.
• Dihydrogen dichalcogenides (H2X2) have been proposed as candidates for observing these effects.

Purpose of the Study:

• To present a quasirelativistic two-component density functional theory (DFT) approach based on the zeroth-order regular approximation (ZORA).
• To compute parity-violating energy differences between enantiomers of dihydrogen dichalcogenides (H2X2).
• To assess the accuracy and efficiency of the ZORA approach compared to four-component relativistic methods.

Main Methods:

• Employed a two-component DFT approach utilizing the zeroth-order regular approximation (ZORA).
• Calculated parity-violating energy differences for P and M conformations of H2X2 (X=O, S, Se, Te, Po).
• Compared ZORA results with pure and hybrid density functionals against relativistic four-component Dirac-Kohn-Sham-Coulomb schemes.

Main Results:

• The DFT ZORA approach with pure functionals showed deviations less than 1% compared to four-component methods.
• Hybrid functionals, like B3LYP, exhibited slightly larger deviations (up to 3% for H2O2, 2% for H2S2, and ≤1% for heavier homologs).
• The ZORA method proved computationally efficient while maintaining high accuracy.

Conclusions:

• The two-component ZORA DFT approach is an excellent and computationally efficient alternative to four-component methods for calculating parity-violating energy differences.
• This method is highly suitable for predicting parity-violating vibrational frequency shifts in chiral molecules.
• The ZORA approach is particularly promising for studying isotopomers of H2Se2 and H2Te2.