Interaction between water and carbon nanostructures: How good are current density functional approximations?

Area of Science:

• Computational chemistry
• Materials science
• Physical chemistry

Background:

• Water adsorption on graphitic sp2-bonded carbon is crucial for water filters and desalination technologies.
• Modeling these systems is challenging due to the importance of London dispersion forces and noncovalent interactions.
• Previous studies have established reference interactions for carbon nanostructures with water.

Purpose of the Study:

• To compile a new benchmark dataset (WaC18) for water-carbon interactions.
• To evaluate the performance of 28 different density functional theory (DFT) approaches.
• To identify the most accurate DFT methods for modeling water adsorption on carbon structures.

Main Methods:

• Creation of the WaC18 benchmark set, including various carbon structures and ice polymorphs interacting with water.
• Testing 28 DFT approaches, encompassing semilocal functionals, nonlocal exchange, and van der Waals (vdW) corrections.
• Calculating deviations from reference interaction energies to assess method performance.

Main Results:

• DFT approach significantly impacts accuracy, with mean absolute deviations ranging from 135 meV (LDA) to 12 meV (PBE0-D4).
• Modern vdW corrections substantially enhance DFT performance compared to older methods.
• PBE0-D4, BLYP-D4, TPSS-D4, and rev-vdW-DF2 identified as top performers in hybrid, GGA, meta-GGA, and vdW-DF classes, respectively.

Conclusions:

• Accurate modeling of water adsorption on carbon materials is achievable with advanced DFT methods.
• The WaC18 benchmark provides a valuable resource for evaluating and improving computational models.
• The findings guide the selection of optimal DFT approaches for applications in water purification and separation.