Numerical comparison of generalized surface hopping, classical analog, and selfconsistent eikonal approximations for nonadiabatic scattering A selfconsistent eikonal treatment of diabatic rearrangement: Model H++H2 calculationsa)We develop an eikonal treatment of electronic transitions in many-atom collisions, in which classical nuclear trajectories are self-consistently coupled to quantal electronic transitions. The treatment starts with a discussion of the electronic representations required to assure that Hamiltonian matrices are Hermitian. The amplitudes of wave functions are found to satisfy coupled equations which are expanded in powers of a local de Broglie wavelength. Time-dependent equations are transformed to derive a Hamiltonian formalism that couples nuclear positions and momenta with electronic amplitUdes. Cross sections are obtained from flux conservation and also from T-matrix elements.(3) 7138

Charge transfer photoinduced by steady light absorption on a silicon surface leads to formation of a surface photovoltage (SPV). The dependence of this voltage on the structure of surface adsorbates and on the wavelength of light is studied with a combination of ab initio electronic structure calculations and the reduced density matrix for the open excited system. Our derivations provide time averages of surface electric dipoles, which follow from a time-dependent density matrix (TDDM) treatment using a steady state solution for the TDDM equations of motion. Ab initio calculations have been carried out in a basis set of Kohn-Sham orbitals obtained by a density functional treatment using atomic pseudopotentials. Applications have been done to a H-terminated Si(111) surface and for adsorbed Ag, with surface coverage ranging from 0 to 3/24 of a monolayer. Calculations done also for amorphous Si agree with measured values of the SPV versus incident photon frequency for H-terminated a-Si. Surface adsorbates are found to enhance light absorption and facilitate electronic charge transfer at the surface. Specifically, Ag clusters add electronic states in the energy gap area, provide stronger absorption in the IR and visible spectral regions, and open up additional pathways for surface charge transfer. Our treatment can be implemented for a wide class of photoelectronic materials relevant to solar energy capture.

Relaxation pathways of photoinduced electronic redistribution at nanostructured semiconductor surfaces are obtained from time-dependent density matrix and ab initio electronic structure methods, giving electronic changes in energy and space over time. They are applied to a Ag cluster on a Si(111) surface, initially photoexcited by a short pulse, and show that the Ag cluster adds surface-localized states that enhance electron transfer. Results on the time evolution of population density distributions in energy and in space, for valence and conduction bands, explore the energy band landscape of a Si slab, with various relaxation pathways ending up in a charge-separated state, with a hole in the Si slab and an electron in the adsorbed Ag cluster. Calculated electronic relaxation times for Si(111)/H are of the same order as experimental values for similar semiconductor systems.

A first-principles study of the stability and optical response of subnanometer silver clusters Agn (n ≤ 5) on a TiO2(110) surface is presented. First, the adequacy of the vdW-corrected DFT-D3 approach is assessed using the domain-based pair natural orbital correlation DLPNO-CCSD(T) calculations along with the Symmetry-Adapted Perturbation Theory [SAPT(DFT)] applied to a cluster model. Next, using the DFT-D3 treatment with a periodic slab model, we analyze the interaction energies of the atomic silver clusters with the TiO2(110) surface. Finally, the hybrid HSE06 functional and a reduced density matrix treatment are applied to obtain the projected electronic density of states and photo-absorption spectra of the TiO2(110) surface, with and without adsorbed silver clusters. Our results show the stability of the supported clusters, the enhanced light absorbance intensity of the material upon their deposition, and the appearance of intense secondary broad peaks in the near-infrared and the visible regions of the spectrum, with positions depending on the size and shape of the supported clusters. The secondary peaks arise from the photo-induced transfer of electrons from intra-band valence 5s orbitals of the noble-metal cluster to 3d Ti band states of the supporting material.

This is an excellent book that can be highly recommended to researchers interested in quantum hydrodynamics and quantum molecular dynamics. The author builds on the Bohm interpretation of quantum mechanics, to present recent developments and applications of quantum trajectories methods, to solve the time-dependent Schrö dinger equation, and to provide a hydrodynamic formulation of quantum dynamics. The subject is of great interest in the study of complex molecular systems, involving many degrees of freedom, and also in connection with the foundations of quantum mechanics. He has managed to give a very readable introduction to the subject in the first four chapters. Two other chapters, written in collaboration with Corey Trahan, deal with details of numerical treatments and give numerical results for model systems. The book proceeds to cover several areas of very active current interest. Among them, Chapter 8 deals with multidimensional dynamics, including nonadiabatic molecular dynamics. Mixed quantum classical dynamics is found in Chapter 12, and topics in quantum hydrodynamics in Chapter 13. Several practical aspects in the calculation of quantum trajectories are covered, including the use of unstructured grids in numerical calculations, grid adaptation, approximations to quantum forces, and propagation of the mechanical stability matrix.Some of the applications have been chosen to illustrate the introductory material, and relate to oscillators and potential barriers. Others involve molecular systems and deal with quantum decoherence in an 11-mode molecule, as well as trajectory surface jumps between two electronic states in a molecule. The book also contains a nice treatment of the density matrix in the Wigner representation and some of the related models including dissipative effects, such as those of Kramer and of Caldeira-Leggett. In addition to covering related literature, this book contains unique topics, relating to quantum trajectories near nodes, Lagrangian chaos, adaptive moving grids, quantum trajectories in phase space, and a quantum Navier-Stokes equation.The author has succeeded in writing a pleasant book, containing not only scientific material, but also pictures and biographic comments about the pioneers on the subjects covered. It contains many graphs, boxes on special topics, and 375 references.

Electronic energy and charge transfer in atomic collisions are described within a first principles molecular dynamics including an explicit treatment of electronic motions, in terms of time-dependent many-electron wavefunctions. Following an overview of treatments in the literature based on expansions in sets of adiabatic and diabatic electronic states, this article emphazises the use of time-dependent molecular orbitals and timedependent Hartree-Fock states. Three fundamental problems are identified in a first principles dynamics, relating to the calculation of state-to-state transition probabilities and expectation values, to the translational motion of electrons moving with nuclei, and to the coupling of fast electronic transitions and slow nuclear motions. Solutions to these problems are described on the basis of an eikonal representation of wavefunctions and sums over initial conditions, of the use of traveling atomic functions to expand molecular orbitals, and of a relax-and-drive propagation procedure for electrons and nuclei. Examples are presented of applications in ion-atom and ion-surface collisions, relating to electronic excitation and charge transfer, orbital polarization, and light emission during collisions.

The dynamics of atoms or molecules adsorbed on a metal surface, and excited by collisions with an atomic beam, are treated within a theory that includes energy dissipation into lattice vibrations by means of a frequency and temperature dependent friction function. The theory provides dynamic structure factors for energy transfer derived from collisional time correlation functions. It describes the relaxation of a vibrationally excited atom or molecule within a model of a damped quantum harmonic oscillator bilinearly coupled to a bath of lattice oscillators. The collisional time correlation function is generalized to include friction effects and is applied to the vibrational relaxation of the frustrated translation mode of Na adsorbed on a Cu͑001͒ surface, CO on Cu͑001͒, and CO on Pt͑111͒, following excitation by collisions with He atoms. Results for the frequency shift and width of line shapes versus surface temperature are in very good agreement with experimental measurements of inelastic He atom scattering. Our interpretation of the experimental results provides insight on the relative role of phonon versus electron-hole relaxation.

The interaction of silicon quantum dots with light is remarkable, as electronic transitions are influenced by the interplay of their atomic structure and by electronic quantum confinement in three dimensions. In this study, the optical properties of 4 undoped and 16 doped silicon quantum dots were calculated using time-dependent density functional theory. The HOMO–LUMO gap, maximum absorption wavelength, and oscillator strength at that wavelength were calculated for two crystalline structures, c-Si29H36 and c-Si35H36, and two amorphous structures, a-Si29H36 and a-Si35H36; in addition, optical properties were calculated for each of the structures doped with either phosphorus or aluminum in one of two different positions: in the center of the cluster or at the surface of the cluster. The calculated optical properties reveal that the absorbance spectrum of the amorphous structures is red shifted compared to that of the crystalline structures, and doping causes the spectrum to shift even further toward the red. Additionally, absorption of light at the maximum wavelength in doped structures caused charge density to transfer from the center of the quantum dot to the surface. The combination of strong absorptions in the visible region of the electromagnetic spectrum and the observed charge transfer make doped silicon quantum dots promising candidates as materials for solar energy applications.