10 research outputs found
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
Nonadiabatic Vibrational Damping of Molecular Adsorbates: Insights into Electronic Friction and the Role of Electronic Coherence
Energy dissipation at metal surfaces
Conversion of energy at the gas–solid interface lies at the heart of many industrial applications such as heterogeneous catalysis. Dissipation of parts of this energy into the substrate bulk drives the thermalization of surface species, but also constitutes a potentially unwanted loss channel. At present, little is known about the underlying microscopic dissipation mechanisms and their (relative) efficiency. At metal surfaces, prominent such mechanisms are the generation of substrate phonons and the electronically non-adiabatic excitation of electron–hole pairs. In recent years, dedicated surface science experiments at defined single-crystal surfaces and predictive-quality first-principles simulations have increasingly been used to analyze these dissipation mechanisms in prototypical surface dynamical processes such as gas-phase scattering and adsorption, diffusion, vibration, and surface reactions. In this topical review we provide an overview of modeling approaches to incorporate dissipation into corresponding dynamical simulations starting from coarse-grained effective theories to increasingly sophisticated methods. We illustrate these at the level of individual elementary processes through applications found in the literature, while specifically highlighting the persisting difficulty of gauging their performance based on experimentally accessible observables
Energy Dissipation during Diffusion at Metal Surfaces: Disentangling the Role of Phonons versus Electron-Hole Pairs
Nano‐Scale Complexions Facilitate Li Dendrite‐Free Operation in LATP Solid‐State Electrolyte
Dendrite formation and growth remains a major obstacle toward high-performance all solid-state batteries using Li metal anodes. The ceramic Li(1+x)Al(x)Ti(2−x)(PO4)3 (LATP) solid-state electrolyte shows a higher than expected stability against electrochemical decomposition despite a bulk electronic conductivity that exceeds a recently postulated threshold for dendrite-free operation. Here, transmission electron microscopy, atom probe tomography, and first-principles based simulations are combined to establish atomistic structural models of glass-amorphous LATP grain boundaries. These models reveal a nanometer-thin complexion layer that encapsulates the crystalline grains. The distinct composition of this complexion constitutes a sizable electronic impedance. Rather than fulfilling macroscopic bulk measures of ionic and electronic conduction, LATP might thus gain the capability to suppress dendrite nucleation by sufficient local separation of charge carriers at the nanoscale
Programmed Death-Ligand 1 Heterogeneity and Its Impact on Benefit From Immune Checkpoint Inhibitors in NSCLC
Increased expression of adenosine 2A receptors in metastatic renal cell carcinoma is associated with poorer response to anti-vascular endothelial growth factor agents and anti-PD-1/Anti-CTLA4 antibodies and shorter survival
Multiple roles for the actin cytoskeleton during regulated exocytosis
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e. secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules