Restoring size consistency of approximate functionals constructed from the adiabatic connection

TL;DR

This paper addresses the size-consistency flaw in approximate exchange-correlation functionals derived from the adiabatic connection in density functional theory, proposing a simple correction method that improves accuracy in molecular interaction energy calculations.

Contribution

The authors introduce a straightforward, computationally inexpensive correction to restore size consistency in AC-based functionals, enhancing their reliability for molecular interaction energies.

Findings

Size consistency can be restored without additional computational cost.

AC-based functionals outperform second-order perturbation theory in accuracy.

The correction improves the reliability of density functional approximations for molecular systems.

Abstract

Approximate exchange-correlation functionals built by modeling in a non-linear way the adiabatic connection (AC) integrand of density functional theory have many attractive features, being virtually parameters-free and satisfying different exact properties, but they also have a fundamental flaw: they violate the size-consistency condition, crucial to evaluate interaction energies of molecular systems. We show that size consistency in the AC-based functionals can be restored in a very simple way at no extra computational cost. Results on a large set of benchmark molecular interaction energies show that functionals based on the interaction strength interpolation approximations are significantly more accurate than the second-order perturbation theory.