Molecular orbital projectors in non-empirical jmDFT recover exact conditions in transition metal chemistry

TL;DR

This paper introduces a molecular orbital projector basis for non-empirical jmDFT, significantly reducing errors in transition metal chemistry modeling by accurately capturing static correlation and delocalization effects.

Contribution

It develops a molecular orbital projector approach for jmDFT that outperforms traditional atomic orbital projectors in transition metal complexes.

Findings

MOP basis nearly eliminates energetic delocalization and static correlation errors.

jmDFT with MOP outperforms AOP jmDFT in all tested cases.

Non-empirical jmDFT reduces flat plane errors effectively.

Abstract

Low-cost, non-empirical corrections to semi-local density functional theory are essential for accurately modeling transition metal chemistry. Here, we demonstrate the judiciously-modified density functional theory (jmDFT) approach with non-empirical U and J parameters obtained directly from frontier orbital energetics on a series of transition metal complexes. We curate a set of nine representative Ti(III) and V(IV) $d^1$ transition metal complexes and evaluate their flat plane errors along the fractional spin and charge lines. We demonstrate that while jmDFT improves upon both DFT+U and semi-local DFT with the standard atomic orbital projectors (AOPs), it does so inefficiently. We rationalize these inefficiencies by quantifying hybridization in the relevant frontier orbitals for both the case of fractional spins and fractional charges. To overcome these limitations, we introduce a procedure for computing a molecular orbital projector (MOP) basis for use with jmDFT. We demonstrate this single set of $d^1$ MOPs to be suitable for nearly eliminating all energetic delocalization error and static correlation error. In all cases, the MOP jmDFT outperforms AOP jmDFT, and it eliminates most flat plane errors at non-empirical values. Unlike widely employed DFT+U or hybrid functionals, jmDFT nearly eliminates energetic delocalization error and static correlation error within a non-empirical framework.