Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory

Abstract

We present a framework for obtaining reliable solid-state charge and optical excitations and spectra from optimally-tuned range-separated hybrid density functional theory. The approach, which is fully couched within the formal framework of generalized Kohn-Sham theory, allows for accurate prediction of exciton binding energies. We demonstrate our approach through first principles calculations of one-and two-particle excitations in pentacene, a molecular semiconducting crystal, where our work is in excellent agreement with experiments and prior computations. We further show that with one adjustable parameter, set to produce an accurate bandgap, this method accurately predicts band structures and optical spectra of silicon and lithium flouride, prototypical covalent and ionic solids. Our findings indicate that for a broad range of extended bulk systems, this method may provide a computationally inexpensive alternative to many-body perturbation theory, opening the door to studies of materials of increasing size and complexity.

Nonempirical dielectric-dependent hybrid functional with range separation for semiconductors and insulators

“…At variance with the bootstrap kernel, the f xc in Ref. [56] is evaluated directly as the functional derivative of the xc potential, thereby approximately capturing the excitonic effect through the nonlocal exchange included in the hybrid functional [55,63,[149][150][151]. More calculations, preferably using a more rigorous f xc kernel [152], are needed to elucidate the efficacy of the approximate f xc kernels for the DDHs.…”

“…For molecular systems, an optimal tuning scheme for the mixing parameter based on the idea of range separation was proposed by enforcing the Koopmans' condition [52,53]. The scheme was later adapted to extended systems [54,55]. In the more recent range-separated DDH (RS-DDH) of Skone et al [56], the screening length of Fock exchange is determined through the dielectric function calculated from first principles.…”

Low-lying excited states in crystalline perylene

“…Theoretical studies of excited-state properties have been performed for acenes (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), such as pentacene, and related Significance Molecular solids are an important class of highly tunable, chemically diverse, cheap-to-process materials with promise for nextgeneration organic optoelectronics. Bound largely by noncovalent interactions, these materials harbor unique charge carrier generation and transport phenomena distinct from conventional semiconductors, an understanding of which requires a detailed description of the excited-state properties of molecular solids.…”

Excitons in Solids from Time-Dependent Density-Functional Theory: Assessing the Tamm-Dancoff Approximation

“…First, our conclusions hold only for LRC-type kernels designed for solids. We did not check the effect of the TDA on other types of methods that account for bound excitons in solids (such as the reverse-engineered BSE kernel [2,4], meta-generalized gradient approximations (meta-GGAs) [34] or hybrid xc kernels [12,[35][36][37][38]) or are designed for atoms and molecules (some discussion of the TDA in the latter case can be found in Ref. [39]).…”