Detection and Correction of Delocalization Errors for Electron and Hole Polarons Using Density-Corrected DFT

Abstract

Modeling polaron defects is an important aspect of computational materials science, but the description of unpaired spins in density functional theory (DFT) often suffers from delocalization error. To diagnose and correct the overdelocalization of spin defects, we report an implementation of density-corrected (DC-)DFT and its analytic energy gradient. In DC-DFT, an exchange-correlation functional is evaluated using a Hartree−Fock density, thus incorporating electron correlation while avoiding selfinteraction error. Results for an electron polaron in models of titania and a hole polaron in Al-doped silica demonstrate that geometry optimization with semilocal functionals drives significant structural distortion, including the elongation of several bonds, such that subsequent single-point calculations with hybrid functionals fail to afford a localized defect even in cases where geometry optimization with the hybrid functional does localize the polaron. This has significant implications for traditional workflows in computational materials science, where semilocal functionals are often used for structure relaxation. DC-DFT calculations provide a mechanism to detect situations where delocalization error is likely to affect the results.

How Good Is the Density-Corrected SCAN Functional for Neutral and Ionic Aqueous Systems, and What Is So Right about the Hartree–Fock Density?

“…Instead of improving the FLOSIC method, in this study we follow an alternative route by using density-corrected DFT (DC-DFT) to tackle density-driven errors in aqueous systems. DC-DFT − replaces the Kohn–Sham density with a more accurate density in a non-self-consistent fashion. In practice, the most common flavor of DC-DFT is HF-DFT in which a DFA is evaluated on the HF electron density.…”

Computational Chemistry as Applied in Environmental Research: Opportunities and Challenges

“…261,348−354 Several method constructs have been developed to address these limitations, such as Grimme's dispersion correction (D3), 355 range-separated functionals, 356 and density-corrected DFT methods. 357 Conceptual flowcharts to aid in the decision-making process of computational chemistry approaches are available in the literature. 347 Also, while accurate in many instances, some specific (and environmentally relevant) problems have been proven to be difficult for ab initio methods.…”

“…Thus, selecting a reasonable, efficient, and accurate quantum chemistry treatment is intricate . It is known that traditional DFT methods (e.g., B3LYP/6-31G*) suffer from errors arising from incomplete electron correlation treatment, electron delocalization, spin-state energetics, incorrect metal–ligand and conformational structural parameters, and the treatment of weak interactions and dispersion forces. ,− Several method constructs have been developed to address these limitations, such as Grimme’s dispersion correction (D3), range-separated functionals, and density-corrected DFT methods . Conceptual flowcharts to aid in the decision-making process of computational chemistry approaches are available in the literature .…”

Radicals in aqueous solution: assessment of density-corrected SCAN functional

“…8 While the theoretical framework for a variational formulation of DC-DFT has been proposed for some time, 21 its widespread implementation in quantum chemistry codes is still limited. 22 However, the availability of analytical forces in DC-DFT would offer significant advantages, as it not only addresses the challenge of self-consistency but also improves standard DFT forces and geometries in density-sensitive calculations. The wider adoption of such implementations would enable comprehensive investigations into the performance of DC-DFT in terms of both geometries and energies.…”