On the electron leak problem in orbital-free embedding calculations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Simulating large systems with quantum mechanics is computationally expensive.
• Hybrid quantum mechanics/molecular mechanics (QM/MM) methods often use orbital-free descriptions for some parts, leading to artificial charge transfer.
• Maintaining charge conservation is crucial for accurate simulations.

Purpose of the Study:

• To investigate the charge leakage problem in subsystem density functional theory (DFT) calculations.
• To assess the validity of DFT subsystem methods for systems with varying levels of description.
• To demonstrate the robustness of DFT subsystem formulation for intermolecular complexes.

Main Methods:

• Utilizing the subsystem formulation of density functional theory (DFT).
• Performing calculations on intermolecular complexes, specifically F(-)H(2)O and Li(+)H(2)O.
• Analyzing the charge distribution and transfer between subsystems with and without explicit orbital descriptions.

Main Results:

• The absence of explicit orthogonality conditions between orbitals of different subsystems did not lead to artificial charge leakage.
• DFT subsystem methods successfully described intermolecular complexes where charge leakage was anticipated.
• Accurate charge distribution was maintained despite the differing descriptions of subsystems.

Conclusions:

• Density functional theory (DFT) subsystem formulation is a reliable method for simulating complex systems.
• This approach effectively mitigates the artificial charge leakage problem in hybrid simulations.
• The method is particularly suitable for studying intermolecular interactions in various chemical and biological systems.