Using Density-Corrected DFT to Understand Density-Driven and Functional-Dependent Errors in Ab Initio Simulations of...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Mechanics

Background:

• The hydrated electron is vital in chemical processes, necessitating accurate theoretical modeling.
• Density Functional Theory (DFT) is used for simulating hydrated electrons but suffers from density-driven errors (DDEs) in anionic systems.
• Density-corrected DFT (DC-DFT) aims to mitigate DDEs by using Hartree-Fock (HF) densities.

Purpose of the Study:

• To investigate the impact of DC-DFT on the properties of the hydrated electron.
• To assess whether DC-DFT reduces DDEs in hydrated electron simulations.
• To compare DC-DFT results with experimental data and standard DFT calculations.

Main Methods:

• Simulations of a model hydrated electron water cluster (Kevan structure) with a sulfur atom to analyze charge delocalization.
• Propagation of molecular dynamics trajectories for the hydrated electron using DC-DFT.
• Comparison of calculated properties (e.g., radius of gyration) with experimental measurements.

Main Results:

• DC-DFT successfully reduced density-driven errors in the simulated hydrated electron system.
• Density correction led to further localization of electron density and a tighter solvation structure.
• Despite reducing DDEs, DC-DFT resulted in poorer agreement with experimental observables compared to standard DFT.

Conclusions:

• DC-DFT mitigates DDEs in hydrated electron simulations but does not improve experimental agreement.
• The worsened agreement is attributed to the removal of a fortuitous error cancellation in the PBEh functional.
• Challenges in simulating hydrated electrons with DFT stem from inherent functional approximations, not solely DDEs.