arXiv subjects

Benjamin G. Janesko

Publications and source records attributed to Benjamin G. Janesko.

8 recordsLinked to original sources

arXiv2026

Restoring the uniform density limit in Perdew-Zunger self-interaction correction

The Perdew-Zunger self-interaction correction (PZ-SIC) makes approximate density functionals exact for all one-electron densities, but sacrifices exactness for uniform densities. I show that an alternative to the orbital density ansatz employed in PZ-SIC restores the uniform density limit. The new ansatz also eliminates the need to evaluate approximate density functionals on lobed one-electron densities extracted from smooth many-electron densities, thereby reducing orbital dependence and lobed density error. I demonstrate the alternative ansatz in a broadly accurate nonempirical locally scaled self-interaction-corrected generalized gradient approximation.

physics.comp-ph↗

arXiv2025

Simulating one hundred entangled atoms using projected-interacting full configuration interaction wavefunctions corrected by projected density functionals

Simulating entangled atoms is a prerequisite to modeling quantum materials and remains an outstanding challenge for theory. I introduce a correlated wavefunction approach capable of simulating large entangled systems, and demonstrate its application to a 300-electron active space. Projected-interacting full configuration interaction plus density functional theory PiFCI+DFT combines near-exact correlated wavefunctions of multiple partially-interacting model systems, each corrected by a formally exact density functional. This approach can access large active spaces and visualize entanglement and strong correlation while maintaining competitive accuracy for molecular properties.

physics.chem-ph↗

arXiv2023

DFT+U Type Strong Correlation Functional Derived from Multiconfigurational Wavefunction Theory

We present a DFT+U-type functional for strong correlation, derived from multiconfigurational wavefunction theory. The reference system experiences electron-electron interactions only in DFT+U-type atomic states, yielding a block-localized configuration interaction Hamiltonian which depends on the atomic state occupancies and the promotion energies of doubly excited determinants. Simple approximations for the promotion energies recover the flat-plane condition and provide beyond-zero-sum accuracy for iron spin-crossover complexes.

physics.chem-ph↗

arXiv2022

Projected Hybrid Density Functionals: Method and Application to Core Electron Ionization

This work presents a new class of hybrid density functional theory (DFT) approximations, incorporating nonlocal exact exchange in predefined states such as core atomic orbitals (AOs). These projected hybrid density functionals are a flexible generalization of range-separated hybrids. This work derives projected hybrids using the Adiabatic Projection formalism. One projects the electron-electron interaction operator onto the chosen predefined states, reintroduces the projected operator into the noninteracting Kohn-Sham reference system, and introduces a density functional approximation for the remaining electron-electron interactions. Projected hybrids are readily implemented existing density functional codes, requiring only a projection of the one-electron density matrices and exchange operators entering existing routines. This work also presents a first application: a core-projected Perdew-Burke-Ernzerhof hybrid PBE0c70, in which the fraction of nonlocal exact exchange is increased from 25% to 70% in core AOs. Automatic selection of the projected AOs provides a black-box model chemistry appropriate for both core and valence electron properties. PBE0c70 predicts core orbital energies that accurately recover core-electron binding energies of second- and third-row elements, without degrading PBE0's good performance for valence-electron properties.

physics.chem-ph↗

arXiv2022

Unification of Perdew-Zunger Self-Interaction Correction, DFT+U, and Rung 3.5 Density Functionals

We unify the Perdew-Zunger self-interaction correction (PZSIC) to approximate density functional theory (DFT), the Hubbard correction DFT+U, and Rung 3.5 functionals within the Adiabatic Projection formalism. We modify the Kohn-Sham reference system, introducing electron self-interaction in selected states. Choosing those states as localized orbitals, localized atomic states, or states at each point in space recovers PZSIC, DFT+U, and Rung 3.5. Typical Hubbard U parameters approximate scaled-down PZSIC. A Rung 3.5 variant of DFT+U opens a band gap in the homogeneous electron gas.

physics.chem-ph↗

arXiv2022

Systematically Improvable Generalization of Self-Interaction Corrected Density Functional Theory

Perdew-Zunger self-interaction correction (PZSIC) reintroduces an exact constraint to approximate density functional theory (DFT), but can paradoxically degrade performance and is not systematically improvable. We use the Adiabatic Projection formalism to derive PZSIC in terms of a reference system experiencing only electron self-interaction. Generalization introduces correlation into the reference system, systematically bridging from PZSIC to exact wavefunction theory. Minimal active spaces resolve the PZSIC paradox, accurately treating near-equilibrium and strongly-correlated systems.

physics.chem-ph↗

arXiv2009

Long-range-corrected hybrids including RPA correlation

We recently demonstrated a connection between the random phase approximation (RPA) and coupled cluster theory [J. Chem. Phys. 129, 231101 (2008)]. Based on this result, we here propose and test a simple scheme for introducing long-range RPA correlation into density functional theory. Our method provides good thermochemical results and models van derWaals interactions accurately.

cond-mat.mtrl-sci↗

arXiv2004

Using molecular similarity to construct accurate semiempirical electron structure theories

Ab initio electronic structure methods give accurate results for small systems, but do not scale well to large systems. Chemical insight tells us that molecular functional groups will behave approximately the same way in all molecules, large or small. This molecular similarity is exploited in semiempirical methods, which couple simple electronic structure theories with parameters for the transferable characteristics of functional groups. We propse that high-level calculations on small molecules provide a rich source of parametrization data. In principle, we can select a functional group, generate a large amount of ab initio data on the group in various small-molecule environments, and "mine" this data to build a sophisticated model for the group's behavior in large molecules. This work details such a model for electron correlation: a semiempirical, subsystem-based correlation functional that predicts a subsystem's two-electron density as a functional of its one-electron density. This model is demonstrated on two small systems: chains of linear, minimal-basis (H-H)5, treated as a sum of four overlapping (H-H)2 subsystems; and the aldehyde group of a set of HOC-R molecules. The results provide an initial demonstration of the feasibility of this approach.

physics.chem-ph↗