A molecular dynamics study of the hydroxyl radical in solution applying self-interaction-corrected density functional...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Theoretical Chemistry

Background:

• Density Functional Theory (DFT) is a powerful tool for molecular simulations.
• Self-interaction error (SIE) can affect the accuracy of DFT calculations, particularly for open-shell systems like the hydroxyl radical (*OH).
• Generalized Gradient Approximation (GGA) methods, while common, may introduce artifacts due to SIE.

Purpose of the Study:

• To investigate the solvation of the hydroxyl radical (*OH) in solution using DFT with Self-Interaction Corrected (SIC) methods.
• To evaluate a new empirical SIC functional against existing methods and reference calculations.
• To provide a more accurate description of *OH solvation and its interactions with water molecules.

Main Methods:

• Ab initio molecular dynamics (MD) simulations based on DFT.
• Application of a restricted open-shell formulation with SIC, including two established correction formulas and a novel empirical functional.
• Validation of the new functional using gas-phase radical cation and hydroxyl water dimers.

Main Results:

• SIC-based MD simulations reveal a different solvation structure for *OH compared to GGA.
• The artifactual hemibonded water observed in GGA simulations is absent with SIC methods.
• *OH primarily acts as a hydrogen bond donor, accepting fewer than two hydrogen bonds on average.
• The solvation shell is characterized by mobile hydrogen bonds and a quasi-hydrophobic cage.

Conclusions:

• The proposed SIC scheme offers a computationally efficient and accurate approach for modeling *OH solvation.
• SIC methods can mitigate self-interaction errors, leading to more reliable DFT simulation results.
• This approach may broaden the applicability of DFT to complex chemical systems where SIE is significant.