Adsorption of hydrogen atoms on a single graphite sheet (graphene) has been investigated by first-principles electronic structure means, employing plane-wave based periodic density functional theory. A 5 x surface unit cell adopted to study and multiple adsorptions H atoms. Binding barrier energies for sequential sticking have computed number configurations involving adsorption top carbon We find that binding per atom range from approximately 0.8 1.9 eV, with barriers in the 0.0-0.15 eV. In...

Non-Markovian processes can often be turned Markovian by enlarging the set of variables. Here we show, an explicit construction, how this done for dynamics a Brownian particle obeying generalized Langevin equation. Given arbitrary bath spectral density J(0), introduce orthogonal transformation variables into effective modes, leading stepwise to semi-infinite chain with nearest-neighbor interactions. The is uniquely determined J(0) and defines sequence {J(n)}(n∈N) residual densities...

Two series of self-assembled TiO2 nanotube (NT) arrays were grown by electrochemical anodization on a metallic titanium substrate with different times and applied potentials in HF-containing ethylene glycol electrolyte solutions postcalcined at 450 °C. The obtained thin films characterized FESEM, XRD, UV–vis–NIR DRS analyses tested as photoanodes incident photon to current efficiency (IPCE) measurements two-compartment photoelectrochemical cell (PEC) for separate H2 O2 production....

We study $n\ifmmode\times\else\texttimes\fi{}n$ honeycomb superlattices of defects in graphene. The considered are missing ${p}_{z}$ orbitals and can be realized by either introducing C atom vacancies or chemically binding simple atomic species at the given sites. Using symmetry arguments electronic-structure calculations we show that it is possible to open a band gap without breaking graphene point symmetry. This has advantage new Dirac cones appear right close gapped region. find induced...

Following up on our recent study of ultrafast charge separation at oligothiophene-fullerene interfaces [H. Tamura, I. Burghardt, and M. Tsukada, J. Phys. Chem. C 115, 10205 (2011)10.1021/jp203174e], we present here a detailed quantum dynamical perspective the transfer process. To this end, electron-phonon coupling is included non-perturbatively, by an explicit treatment using multi-configuration time-dependent Hartree (MCTDH) method. Based upon distribution couplings determined from...

We investigate graphene superlattices of nitrogen and boron substitutional defects. Using symmetry arguments electronic structure calculations we show how such can be used to modify band structure. Specifically, depending on the superlattice symmetry, structures considered here either preserve Dirac cones (D6h superlattices) or open a gap (D3h). Relevant parameters (carrier effective masses, group velocities, gaps, when present) are found depend constant n as 1/np where p is in range 1−2,...

Correlated, counterpoise corrected wave function calculations on the hydrogen−coronene system are used to investigate energy landscape and dynamic behavior of hydrogen atoms physisorbed graphite. The adopted MP2 correlation level, employing aug-cc-pVDZ basis set augmented with bond functions, has been selected after extensive investigation smaller hydrogen−benzene system. computed physisorption (39.7 meV) is in excellent agreement existing experimental value (39.2 ± 0.5) meV for a graphite...

Abstract Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations application derive from insolubility, scarce processability chain‐end effects. This study describes an easy access to chiral cyclic constituted by 12 18 fully thiophene units. Chemical oxidation “inherently chiral” sexithiophene monomer, synthesized two steps commercially available materials, induces the...

The simulation of quantum dynamics calls for algorithms working in first quantized grid encodings. Here, we propose a variational algorithm performing quantization. In addition to the usual reduction circuit depth conferred by approaches, this also enjoys several advantages compared previously proposed ones. For instance, approaches suffer from need large number measurements. However, encoding Hamiltonians only requires measuring position and momentum bases, irrespective system size. Their...

Recent years have witnessed an ever growing interest in the interactions between hydrogen atoms and a graphene sheet. Largely motivated by possibility of modulating electric, optical magnetic properties graphene, huge number studies appeared recently that added to enlarged earlier investigations on graphite other carbon materials. In this review we give glimpse many facets adsorption process, as they emerged from these studies. The focus is those issues been addressed detail, under carefully...

Three-dimensional potential energy surfaces (PESs) have been computed, and numerically fitted, for the two lowest electronic states of LiH2+ system, which are importance astrophysically relevant LiH++H→Li++H2 LiH+H+→Li+H2+ exoergic reactions. We extend recently computed 11 000 multi reference valence bond ab initio values [Martinazzo et al., Chem. Phys. 287, 335 (2003)] with 600 multireference configuration interaction calculations complete active self-consistent field functions a large...

Superhydrogenated polycyclic aromatic hydrocarbon (PAH) molecules have been demonstrated to act as catalysts for molecular hydrogen formation under interstellar conditions. Here we present combined thermal desorption mass spectrometry measurements and density functional theory calculations that reveal the most stable configurations in superhydrogenation sequence of PAH molecule coronene (C24H12). Specifically, experiments demonstrate presence superhydrogenated at specific hydrogenation...

A reduced-dimensional effective-mode representation is developed in order to efficiently describe excited-state dynamics of multichromophoric donor-acceptor aggregates within a linear vibronic coupling model. Specifically, we consider systems where vibrational modes pertaining given molecular fragment couple both local excitations Frenkel type and delocalized states charge transfer exciton type. hierarchical chain constructed which suitable correlated fluctuations, leading set spectral...

The McLachlan "minimum-distance" principle for optimizing approximate solutions of the time-dependent Schrodinger equation is revisited, with a focus on local-in-time error accompanying variational solutions. Simple, exact expressions are provided this error, which then evaluated in illustrative cases, notably widely used mean-field approach and adiabatic quantum molecular dynamics. These findings pave way rigorous development adaptive schemes that re-size on-the-fly underlying manifold thus...

A theory of electronic friction is developed using the exact factorization electronic-nuclear wave function. No assumption made regarding bath, which can be independent or interacting electrons, and nuclei are treated quantally. The ensuing equation motion for nuclear function a nonlinear Schrödinger including term. resulting kernel agrees with previously derived mixed quantum-classical result by Dou et al., [Phys. Rev. Lett. 119, 046001 (2017)]PRLTAO0031-900710.1103/PhysRevLett.119.046001,...

The fate of the molecular geometric phase in an exact dynamical framework is investigated with help factorization wave function and a recently proposed quantum hydrodynamical description its dynamics. An instantaneous, gauge-invariant introduced for arbitrary paths nuclear configuration space terms variables, shown to reduce adiabatic when state path closed. evolution closed-path over time adhere Maxwell-Faraday induction law, nonconservative forces arising from electron dynamics that play...

A novel quantum method to deal with typical system-bath dynamical problems is introduced. Subsystem discrete variable representation and bath coherent-state sets are used write down a multiconfigurational expansion of the wave function whole system. With help Dirac-Frenkel variational principle, simple equations motion—a kind Schrödinger-Langevin equation for subsystem coupled (pseudo) classical bath—are derived. True dissipative dynamics at all times obtained by coupling secondary, Ohmic...

Collision induced (CI) processes involving hydrogen atoms on a graphite surface are studied quantum mechanically within the rigid, flat approximation, using time-dependent wave packet method. The Eley-Rideal (ER) reaction and collision desorption (CID) cross sections obtained with help of two propagations which use different sets coordinates, "product" "reagent" set. Several adsorbate-substrate initial states target H atom in chemisorption well considered, CI over wide range projectile...

We investigated binding of hydrogen atoms to small polycyclic aromatic hydrocarbons (PAHs)--i.e., graphene dots with hydrogen-terminated edges--using density functional theory and correlated wavefunction techniques. considered a number PAHs three seven hexagonal rings computed energies for most the symmetry unique sites, along minimum energy paths significant cases. The chosen are enough not present radical character at their edges, yet show clear preference adsorption edge sites which can...

We investigate the details of electronic structure in neighborhoods a carbon atom vacancy graphene by employing magnetization-constrained density-functional theory on periodic slabs, and spin-exact, multireference, second-order perturbation finite cluster. The picture that emerges is two local magnetic moments (one $\ensuremath{\pi}$-like one $\ensuremath{\sigma}$-like) decoupled from $\ensuremath{\pi}$ band coupled to each other. find ground state triplet with planar equilibrium geometry...

Hydrogen formation is a key process for the physics and chemistry of interstellar clouds. Molecular hydrogen believed to form on carbonaceous surface dust grains, several mechanisms have been invoked explain its abundance in different regions space, from cold clouds warm photon-dominated regions. Here, we investigate direct (Eley–Rideal) recombination including lattice dynamics, corrugation, competing H-dimers by means ab initio molecular dynamics. We find that Eley–Rideal reaction dominates...

Circular dichroism (CD) and ultraviolet absorption (UV) spectra of films obtained by electrochemical polymerization inherently chiral 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene (T4-BT2) are taken during polarization cycles. Besides the bisignate CD features in near UV range recorded at zero potential, new visible–near-infrared observed under increased applied potential. Results interpreted with help static time-dependent (TD) density functional theory (DFT) calculations, which shed...