DFT and spatial confinement: a benchmark study on the structural and electrical properties of hydrogen bonded...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate prediction of electrical properties for hydrogen bonded (HB) systems is crucial for understanding molecular interactions and designing new materials.
• Density Functional Theory (DFT) offers a computationally efficient approach, but its accuracy depends heavily on the chosen exchange-correlation functional.
• Spatial confinement effects can significantly alter molecular properties, necessitating studies under realistic conditions.

Purpose of the Study:

• To comprehensively evaluate the performance of 37 DFT exchange-correlation functionals for predicting electrical properties of spatially confined HB dimers.
• To assess the accuracy of DFT methods in describing dipole moments, polarizabilities, hyperpolarizabilities, and their interaction-induced counterparts under confinement.
• To investigate the impact of spatial confinement on the predictive power of DFT functionals and identify the most reliable methods.

Main Methods:

• Evaluation of 37 DFT functionals against CCSD(T) reference data for confined HB dimers.
• Utilized a two-dimensional harmonic oscillator potential to simulate spatial restriction.
• Calculated dipole moment (μz), polarizability (αzz), first hyperpolarizability (βzzz), and interaction-induced properties (Δμz, Δαzz, Δβzzz).

Main Results:

• Most DFT functionals accurately predict dipole moments (μz) and polarizabilities (αzz), as well as their interaction-induced counterparts (Δμz, Δαzz).
• Describing nonlinear optical response (βzzz, Δβzzz) is a significant challenge for many DFT functionals, with some exhibiting catastrophic failures.
• Higher Hartree-Fock exchange generally improves predictions for αzz and Δαzz, while ωB97X-D shows the most consistent accuracy across properties and structural parameters.

Conclusions:

• DFT methods are reliable for calculating μz, αzz, Δμz, and Δαzz of confined HB dimers, with minor errors.
• Accurate prediction of nonlinear optical properties (βzzz, Δβzzz) remains a challenge for most DFT functionals.
• The ωB97X-D functional demonstrates superior overall performance for both electrical properties and structural parameters under confinement, making it a highly recommended choice.