The study of isolated defects in solids is a natural target for classical or quantum embedding methods that treat the defect at high level theory and rest solid lower theory. Here, context active-space-based embeddings, we performance three active-space orbital selection schemes based on canonical (energy-ordered) orbitals, local orbitals defined spirit density matrix theory, approximate transition orbitals. Using equation-of-motion coupled-cluster with single double excitations (CCSD),...

This article describes the functions and mechanisms of particle electron ratchets, interplay between theory experiment in this field non-equilibrium transport.

Compared to common density functionals, ab initio wave function methods can provide greater reliability and accuracy, which could prove useful when modeling adsorbates or defects of otherwise periodic systems. However, the breaking translational symmetry necessitates large supercells that are often prohibitive for correlated methods. As an alternative, this paper introduces regional embedding approach, enables treatments only a target fragment interest through small, fragment-localized...

This paper describes the enhancement of quantum yield photoluminescence (PL) CdSe dots (QDs) upon adsorption an exciton-delocalizing ligand, phenyldithiocarbamate. Increasing apparent excitonic radius by only 10% increases value radiative rate constant a factor 1.8 and PL 2.4. Ligand exchange therefore simultaneously perturbs confinement energy charge carriers enhances probability band-edge transitions.

Displacement of cadmium oleate (Cd(oleate)2) ligands for the exciton-delocalizing ligand 4-hexylphenyldithiocarbamate (C6-PTC) on surfaces CdS quantum dots (QDs) causes a decrease in band gap (Eg) QD ∼100 meV QDs with radius 1.9 nm and ∼50 2.5 nm. The primary mechanism this gap, deduced previous work, is confinement barrier excitonic hole. increase apparent that corresponds to Eg denoted ΔR. dependence ΔR surface coverage C6-PTC, measured by 1H NMR spectroscopy, appears be nonlinear....

Displacement of native octylphosphonate (OPA) ligands for methylthiophenolate (CH3-TP) on the surfaces CdSe quantum dots (QDs) causes a moderate (up to 50 meV) decrease in band gap (Eg) QD. Plots corresponding increase apparent excitonic radius, ΔR, QDs versus surface coverage CH3-TP, measured by 1H NMR, several sizes reveal that this ligand adsorbs two distinct binding modes, (1) tightly bound mode (Ka = 1.0 ± 0.3 × 104 M–1) capable exciton delocalization, and (2) more weakly 8.3 9.9 102...

Significance Transport of objects in man-made systems typically relies on energy gradients that span the distance over which particles must travel. Biological do not have these large-scale available and instead transport with repeated local interactions between asymmetric structures, powered by nondirectional sources like heat or chemical reactions. This process is called “ratcheting.” Here, we exploit ratcheting mechanism to charge-carrying particles, electrons, through an amorphous organic...

Biological systems utilize a combination of asymmetry, noise, and chemical energy to produce motion in the highly damped environment cell with molecular motors, many which are "ratchets", nonequilibrium devices for producing directed transport using nondirectional perturbations without net bias. The underlying ratchet principle has been implemented man-made micro- nanodevices charged particles by oscillating an electric potential repeating asymmetric features. In this experimental study,...

Electron ratchets are non-equilibrium electronic devices that break inversion symmetry to produce currents from non-directional and random perturbations, without an applied net bias. They characterized by strong parameter dependence, where small changes in operating conditions lead large the magnitude even direction of resulting current. This high sensitivity makes electron attractive research subjects, but leads formidable challenges their deeper study, particularly useful application....

This work describes the quantitative characterization of interfacial chemical and electronic structure CdSe quantum dots (QDs) coated in one five p-substituted thiophenolates (X-TP, X = NH2, CH3O, CH3, Cl, or NO2), dependence this on p-substituent X. 1H NMR spectra mixtures QDs X-TPs yield number bound to surface each QD. The binding data, combination with shift energy first excitonic peak as a function coverage X-TP Raman analysis mixtures, indicate that binds at least three modes, two...

Ratchets rectify the motion of randomly moving particles, which are driven by isotropic sources energy such as thermal and chemical energy, without applying a net, time-averaged force between source drain. This paper describes behavior damped electron, modeled quantum Lindblad master equation, within flashing ratchet (a one-dimensional potential that oscillates flat surface periodic asymmetric surface). By examining complete space all biharmonic shapes large range oscillation frequencies,...

Ratcheting is a mechanism that produces directional transport of particles by rectifying nondirectional energy using local asymmetries rather than net bias in the direction transport. In flashing ratchet, an oscillating force (here, AC field) applied perpendicular to effort explore properties current experimentally realizable ratchet systems, and design new ones, this paper describes classical simulations damped transports charged nanoparticles within layer finite, non-zero thickness. The...

Abstract This paper computationally demonstrates a new photovoltaic mechanism that generates power from incoherent, below‐bandgap (THz) excitations of conduction band electrons in silicon. A periodic sawtooth potential, realized through elastic strain gradients along 100 nm thick Si slab, biases the oscillatory motion excited electrons, which preferentially jump and relax into adjacent period on right to generate net current. The magnitude ratchet current increases with photon energy (20,...

We use excited-state quantum chemistry techniques to investigate the intraband absorption of doped semiconductor nanoparticles as a function doping density, nanoparticle radius, and material properties. Modeling excess electrons interacting confined sphere, we find that excitation evolves from single-particle plasmonic with increasing number at fixed threshold produce plasmon increases density due confinement electron-hole attraction. In addition, passes through an intermediate regime where...

The study of isolated defects in solids is a natural target for classical or quantum embedding methods that treat the defect at high level theory and rest solid lower theory. Here, context active-space-based embeddings, we performance three active-space orbital selection schemes based on canonical (energy-ordered) orbitals, local orbitals defined spirit density matrix theory, approximate transition orbitals. Using equation-of-motion coupled-cluster with single double excitations (CCSD),...

We use excited-state quantum chemistry techniques to investigate the intraband absorption of doped semiconductor nanoparticles as a function doping density, nanoparticle radius, and material properties. The excess electrons are modeled interacting particles confined in sphere. compare predictions various single-excitation theories, including time-dependent Hartree-Fock, random-phase approximation, configuration interaction with single excitations. find that Hartree-Fock most accurately...

Compared to common density functionals, ab initio wave function methods can provide greater reliability and accuracy, which could prove useful when modeling adsorbates or defects of otherwise periodic systems. However, the breaking translational symmetry necessitates large supercells that are often prohibitive for correlated methods. As an alternative, we introduce regional embedding approach, enables treatments only a target fragment interest through small, fragment-localized orbital spaces...