Embedded density functional theory for covalently bonded and strongly interacting subsystems

TL;DR

This paper advances embedded density functional theory by implementing an exact embedding method that accurately captures non-additive kinetic potentials, enabling precise modeling of strongly interacting molecular systems and large-scale molecular crystals.

Contribution

The paper introduces a general implementation of the Exact Embedding method for e-DFT, improving accuracy in strongly interacting subsystems and enabling efficient large-system calculations.

Findings

EE method matches reference Kohn-Sham results

Approximate functionals fail qualitatively

Pairwise NAKP approximation enables scalable computations

Abstract

Embedded density functional theory (e-DFT) is used to describe the electronic structure of strongly interacting molecular subsystems. We present a general implementation of the Exact Embedding (EE) method [J. Chem. Phys. 133, 084103 (2010)] to calculate the large contributions of the non-additive kinetic potential (NAKP) in such applications. Potential energy curves are computed for the dissociation of Li+-Be, CH3-CF3, and hydrogen-bonded water clusters, and e-DFT results obtained using the EE method are compared with those obtained using approximate kinetic energy functionals. In all cases, the EE method preserves excellent agreement with reference Kohn-Sham calculations, whereas the approximate functionals lead to qualitative failures in the calculated energies and equilibrium structures. We also demonstrate an accurate pairwise approximation to the NAKP that allows for efficient parallelization of the EE method in large systems; benchmark calculations on molecular crystals reveal ideal, size-independent scaling of wall-clock time with increasing system size.