Analyzing the errors of DFT approximations for compressed water systems.

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Mechanics

Background:

• Density Functional Theory (DFT) is widely used for materials simulations.
• Accurate modeling of compressed water is crucial for understanding various physical and chemical processes.
• Existing DFT approximations like PBE and BLYP have known limitations for condensed phases.

Purpose of the Study:

• To extensively study the errors of PBE and BLYP DFT approximations for compressed water systems.
• To evaluate the effectiveness of 1- and 2-body error corrections using Gaussian approximation potentials.
• To investigate errors in both compressed liquid water and water clusters.

Main Methods:

• Employed first-principles molecular dynamics simulations for liquid water.
• Utilized Quantum Monte Carlo (QMC) benchmarks for energy calculations.
• Analyzed errors by comparing simulation data with experimental pressure and neutron diffraction data.
• Investigated errors in compressed water clusters (trimer to 27-mer).

Main Results:

• DFT approximations exhibit significant errors for compressed liquid water and clusters.
• Correction for 1- and 2-body errors alone does not sufficiently improve accuracy.
• Beyond-2-body errors contribute substantially to the overall DFT errors.
• A 3-body energy correction method shows promise for reducing remaining errors.

Conclusions:

• Standard DFT approximations require significant corrections for accurate compressed water modeling.
• Beyond-2-body effects are critical and must be accounted for.
• Further development of many-body corrections is needed for high-accuracy DFT simulations of condensed systems.