Nonempirical Range-Separated Hybrid Functional with Spatially Dependent Screened Exchange

Abstract

Electronic structure calculations based on density functional theory (DFT) have successfully predicted numerous ground-state properties of a variety of molecules and materials. However, exchange and correlation functionals currently used in the literature, including semilocal and hybrid functionals, are often inaccurate to describe the electronic properties of heterogeneous solids, especially systems composed of building blocks with large dielectric mismatch. Here, we present a dielectric-dependent range-separated hybrid functional, screened-exchange range-separated hybrid (SE-RSH), for the investigation of heterogeneous materials. We define a spatially dependent fraction of exact exchange inspired by the static Coulomb-hole and screened-exchange (COHSEX) approximation used in many-body perturbation theory, and we show that the proposed functional accurately predicts the electronic structure of several nonmetallic interfaces, three- and two-dimensional, pristine, and defective solids and nanoparticles.

Exceptional Spatial Variation of Charge Injection Energies on Plasmonic Surfaces

“…However, DFT eigenvalues do not (even in principle) correspond to the quasi-particle energies, except the system’s highest occupied state . In practice, much-improved estimates of individual electronic states are obtained with approximate DFT functionals that minimize self-interaction errors, e.g., with optimally tuned range-separated functionals in which the asymptotic form of the nonlocal exchange is attenuated, similar to the application of static screening. ,,− Yet, these methods are typically limited to the mean-field description, and they neglect nonlocality and potentially significant anisotropy of the dynamical screening. Further, the extension to new excited state signatures due to strong couplings between the single electron or hole excitation and the dynamical fluctuations necessitates to go beyond DFT. , …”

Excited State Properties of Point Defects in Semiconductors and Insulators Investigated with Time-Dependent Density Functional Theory

“…We are exploring the possibility of extending our TDDFT calculations by incorporating additional hybrid functionals, possibly leading to an improvement in the description of screening effects in solids, especially in low-dimensional hosts such as two-dimensional hexagonal boron nitride (2D-hBN). 93 Work is in progress to further accelerate TDDFT calculations through the use of density fitting techniques, 124,125 which could enable the direct study of multiple point defects and their interactions in the same supercell. Other interesting future efforts include the implementation of spin-flip TDDFT with the multicollinear formalism to reduce numerical instabilities 126,127 and coupling TDDFT with analytical nuclear forces and molecular dynamics.…”

“…91 The small difference between the TDDFT and QDET results and experiments may originate, at least in part, from the use of the DDH functional, which uses a screening constant corresponding to that of the pristine crystal. We expect that adopting a hybrid functional that incorporates the screening effects of both the host crystal and the defect 93 and at the same time taking into account electron−phonon interaction 94,95 may improve our TDDFT results. The optimized geometry in the excited state using TDDFT analytical nuclear forces and the resulting FC shifts and displacements are in good agreement with the ΔSCF results.…”

On the Structure of Oxygen Deficient Amorphous Oxide Films

“…[99] There have been studies investigating procedures by which one can justify certain choices of the Hartree-Fock exchange fraction (see e.g., refs. [111,112] ), which rely on achieving "piecewise-linearity," a known property of the exact XC functional. Although these do not solve every problem, they are very successful in improving the accuracy of calculations and thereby improving the representation of localized electron states.…”