Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEnergy loss of atoms at metal surfaces due to electron-hole pair excitations: First-principles theory of chemicurrents
148
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A method is presented for calculating electron-hole pair excitation due to an incident atom or molecule interacting with a metal surface. Energy loss is described using an textit{ab initio} approach that obtains a position-dependent friction coefficient for an adsorbate moving near a metal surface from a total energy pseudopotential calculation. A semi-classical forced oscillator model is constructed, using the same friction coefficient description of the energy loss, to describe excitation of the electron gas due to the incident molecule. This approach is applied to H and D atoms incident on a Cu(111) surface, and we obtain theoretical estimates of the `chemicurrents measured by Nienhaus et al [Phys. Rev. Lett. textbf{82}, 446 (1999)] for these atoms incident on the surface of a Schottky diode.
rate research
Read More
The time-dependent, mean-field Newns-Anderson model for a spin-polarised adsorbate approaching a metallic surface is solved in the wide-band limit. Equations for the time-evolution of the electronic structure of the adsorbate-metal system are derived and the spectrum of electronic excitations is found. The behaviour of the model is demonstrated for a set of physically reasonable parameters.
Electron-hole pair creation by an adsorbate incident on a metal surface is described using textit{ab initio} methods. The approach starts with standard first principles electronic structure theory, and proceeds to combine classical, quantum oscillator and time dependent density functional methods to provide a consistent description of the non-adiabatic energy transfer from adsorbate to substrate. Of particular interest is the conservation of the total energy at each level of approximation, and the importance of a spin transition as a function of the adsorbate/surface separation. Results are presented and discussed for H and D atoms incident on the Cu(111) surface.
We investigate some surfaces of a paradigmatic sp bonded metal--namely, Al(110), Al(100), and Al(111)--by means of the electron localization function (ELF), implemented in a first-principle pseudopotential framework. ELF is a ground-state property which discriminates in a very sharp, quantitative, way between different kinds of bonding. ELF shows that in the bulk of Al the electron distribution is essentially jelliumlike, while what happens at the surface strongly depends on packing. At the least packed surface, Al(110), ELF indicates a free-atom nature of the electron distribution in the outer region. The most packed surface, Al(111), is instead at the opposite end, and can be regarded as a jellium surface weakly perturbed by the presence of the ionic cores.
The bulk photovoltaic effect (BPVE) has attracted an increasing interest due to its potential to overcome the efficiency limit of traditional photovoltaics, and much effort has been devoted to understanding its underlying physics. However, previous work has shown that theoretical models of the shift current and the phonon-assisted ballistic current in real materials do not fully account for the experimental BPVE photocurrent, and so other mechanisms should be investigated in order to obtain a complete picture of BPVE. In this Letter, we demonstrate two approaches that enable the ab initio calculation of the ballistic current originating from the electron-hole interaction in semiconductors. Using BaTiO$_3$ and MoS$_2$ as two examples, we show clearly that for them the asymmetric scattering from electron-hole interaction is less appreciable than that from electron-phonon interaction, indicating more scattering processes need to be included to further improve the BPVE theory. Moreover, our approaches build up a venue for predicting and designing materials with larger ballistic current due to electron-hole interactions.
We present results for the optical absorption spectra of small-diameter single-wall carbon and boron nitride nanotubes obtained by {it ab initio} calculations in the framework of time-dependent density functional theory. We compare the results with those obtained for the corresponding layered structures, i.e. the graphene and hexagonal BN sheets. In particular, we focus on the role of depolarization effects, anisotropies and interactions in the excited states. We show that already the random phase approximation reproduces well the main features of the spectra when crystal local field effects are correctly included, and discuss to which extent the calculations can be further simplified by extrapolating results obtained for the layered systems to results expected for the tubes. The present results are relevant for the interpretation of data obtained by recent experimental tools for nanotube characterization such as optical and fluorescence spectroscopies as well as polarized resonant Raman scattering spectroscopy. We also address electron energy loss spectra in the small-q momentum transfer limit. In this case, the interlayer and intertube interactions play an enhanced role with respect to optical spectroscopy.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
