Static Electron Correlation in Anharmonic Molecular Vibrations: A Hybrid TAO-DFT Study

Area of Science:

• Computational chemistry
• Quantum chemistry
• Spectroscopy

Background:

• Accurate prediction of molecular vibrational frequencies is essential for understanding molecular structure and dynamics.
• Static electron correlation poses a challenge for standard computational methods, impacting vibrational frequency predictions.
• Existing methods often struggle with multireference systems and molecules containing heavier elements.

Purpose of the Study:

• To investigate the impact of static electron correlation on molecular vibrational frequencies using a novel computational approach.
• To evaluate the performance of hybrid thermally-assisted-occupation density functional theory (TAO-DFT) for predicting vibrational spectra.
• To assess the method's accuracy for benchmark datasets including multireference systems and second-row elements.

Main Methods:

• Utilized hybrid thermally-assisted-occupation density functional theory (TAO-DFT) calculations.
• Employed the B3LYP and B97-1 functionals within the TAO-DFT framework.
• Compared predicted vibrational frequencies against a benchmark set of experimentally observed data.

Main Results:

• TAO-DFT, using B3LYP and B97-1, significantly improves vibrational frequency predictions by capturing static electron correlation.
• Observed notable shifts in vibrational frequencies for known multireference systems and molecules with second-row elements.
• Demonstrated substantial improvements in predicting hydrogen stretching frequencies across the test set.

Conclusions:

• Static electron correlation, as quantified by TAO-DFT, is vital for accurate vibrational frequency calculations.
• Hybrid TAO-DFT offers a more reliable approach for vibrational spectroscopy, particularly for challenging molecular systems.
• The findings highlight the importance of considering electron correlation effects for precise molecular vibrational analysis.