Non-Adiabatic Vibrational Damping of Molecular Adsorbates: Insights into Electronic Friction and the Role of Electronic Coherence

We present a perturbation approach rooted in time-dependent density-functional theory to calculate electron hole (eh)-pair excitation spectra during the non-adiabatic vibrational damping of adsorbates on metal surfaces. Our analysis for the benchmark systems CO on Cu(100) and Pt(111) elucidates the surprisingly strong influence of rather short electronic coherence times. We demonstrate how in the limit of short electronic coherence times, as implicitly assumed in prevalent quantum nuclear theories for the vibrational lifetimes as well as electronic friction, band structure effects are washed out. Our results suggest that more accurate lifetime or chemicurrent-like experimental measurements could characterize the electronic coherence.Comment: Article as accepted for publication in Physical Review Letter

Electronic friction-based vibrational lifetimes of molecular adsorbates: Beyond the independent atom approximation

We assess the accuracy of vibrational damping rates of diatomic adsorbates on metal surfaces as calculated within the local-density friction approximation (LDFA). An atoms-in-molecules (AIM) type charge partitioning scheme accounts for intra-molecular contributions and overcomes the systematic underestimation of the non-adiabatic losses obtained within the prevalent independent atom approximation. The quantitative agreement obtained with theoretical and experimental benchmark data suggests the LDFA-AIM as an efficient and reliable approach to account for electronic dissipation in ab initio molecular dynamics simulations of surface chemical reactions.Comment: 5 pages including 2 figure

Cosmic Ray Nuclei (CRN) detector investigation

The Cosmic Ray Nuclei (CRN) detector was designed to measure elemental composition and energy spectra of cosmic radiation nuclei ranging from lithium to iron. CRN was flown as part of Spacelab 2 in 1985, and consisted of three basic components: a gas Cerenkov counter, a transition radiation detector, and plastic scintillators. The results of the experiment indicate that the relative abundance of elements in this range, traveling at near relativistic velocities, is similar to those reported at lower energy

Systemic suppression of the shoot metabolism upon rice root nematode infection

Hirschmanniella oryzae is the most common plant-parasitic nematode in flooded rice cultivation systems. These migratory animals penetrate the plant roots and feed on the root cells, creating large cavities, extensive root necrosis and rotting. The objective of this study was to investigate the systemic response of the rice plant upon root infection by this nematode. RNA sequencing was applied on the above-ground parts of the rice plants at 3 and 7 days post inoculation. The data revealed significant modifications in the primary metabolism of the plant shoot, with a general suppression of for instance chlorophyll biosynthesis, the brassinosteroid pathway, and amino acid production. In the secondary metabolism, we detected a repression of the isoprenoid and shikimate pathways. These molecular changes can have dramatic consequences for the growth and yield of the rice plants, and could potentially change their susceptibility to above-ground pathogens and pests

Electron Counting Rules and Electronic Structure in Tetrameric Transition-Metal (T)-Centered Rare-Earth (R) Cluster Complex Halides (X)

Electron partition schemes are a beneficial means to systematize bonding networks and to identify structure-bonding relationships in polar intermetallics. One prolific class of polymetal networks with simple counterions is the broad family of transition-metal (T)-centered rare-earth metal (R) cluster halides (X), which can be isolated or condensed to oligomers and chains. While the electronic structures of R cluster monomers and chains encapsulating T atoms have been studied systematically, the band structures of oligomers, in particular, the most frequent Friauf-type {T4R16} tetramers, have been investigated to a lesser extent. Therefore, the band structures of prototypical compounds with {T4R16}-type tetramers, while maintaining different compositions, were analyzed employing density functional theory based methods. Furthermore, these theoretical examinations provide insight into the origin of the 15 electron rule, which is significant for this class of compounds and correlates with the closed-shell configurations for these structures. Additional research focused on the band structure of monoclinic {Ru4Gd16}Br23, which is composed of rhomboid-shaped {Ru4Gd16} tetramers

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders