GGA-Level Subsystem DFT Achieves Sub-kcal/mol Accuracy Intermolecular Interactions by Mimicking Nonlocal Functionals

TL;DR

This paper introduces a GGA-level subsystem DFT functional that mimics nonlocal behavior, achieving sub-kcal/mol accuracy in intermolecular interactions with computational efficiency.

Contribution

A novel GGA nonadditive kinetic energy functional that replicates nonlocal functional behavior while maintaining semilocal computational complexity.

Findings

Reproduces Kohn-Sham DFT and CCSD(T) interaction energies with high accuracy.

Achieves mean absolute deviation below 1 kcal/mol on benchmark sets.

Maintains computational efficiency comparable to semilocal functionals.

Abstract

The key feature of nonlocal kinetic energy functionals is their ability to reduce to the Thomas-Fermi functional in the regions of high density and to the von Weizs\"acker functional in the region of low density/high density gradient. This behavior is crucial when these functionals are employed in subsystem DFT simulations to approximate the nonadditive kinetic energy. We propose a GGA nonadditive kinetic energy functional which mimics the good behavior of nonlocal functionals retaining the computational complexity of typical semilocal functionals. The new functional reproduces Kohn-Sham DFT and benchmark CCSD(T) interaction energies of weakly interacting dimers in the S22-5 and S66 test sets with a mean absolute deviation well below 1 kcal/mol.