Accurate vibrational hydrogen-bond shift predictions with multicomponent DFT.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Multicomponent methods offer advanced simulation capabilities by simultaneously treating electronic and protonic wave functions.
• Existing methods have limitations in application range, particularly for anharmonic effects and proton vibrations.
• Nuclear-Electronic Orbital Density Functional Theory (NEO-DFT) shows promise for accurately modeling these phenomena.

Purpose of the Study:

• To investigate the performance of NEO-DFT for predicting anharmonic OH vibrational shifts in water complexes.
• To evaluate various Density Functional Theory (DFT) functionals, including hybrid and double-hybrid types.
• To develop a robust prediction strategy for vibrational shifts using readily available computational ingredients.

Main Methods:

• Utilized the expanded HyDRA database, comprising 35 hydrogen-bonded monohydrates of small organic molecules.
• Performed calculations using a range of DFT and double-hybrid functionals within the NEO-DFT framework.
• Introduced a novel prediction strategy leveraging common DFT and NEO-DFT calculation outputs.

Main Results:

• Achieved root mean square deviation (RMSD) values below 10 cm^-1 for the first time on the tested set.
• Identified double-hybrid functionals combined with DFT treatment of protons as particularly effective.
• Validated the methodology on newly added systems within the HyDRA dataset.

Conclusions:

• NEO-DFT provides a powerful tool for simulating anharmonic OH vibrational shifts.
• The developed prediction strategy offers high accuracy and practical applicability.
• Double-hybrid functionals show significant potential for advancing the accuracy of these simulations.