Huffmanlyhne1932

Non-adiabatic molecular dynamics of neutral chrysene and tetracene molecules is investigated using Tully's fewest switches surface hopping algorithm coupled to the time-dependent density functional based tight-binding (TD-DFTB) method for electronic structure calculations. We first assess the performance of two DFTB parameter sets based on the computed TD-DFTB absorption spectra. The main focus is given to the analysis of the electronic relaxation from the brightest excited state following absorption of a UV photon. We determine the dynamical relaxation times and discuss the underlying mechanisms. Our results show that the electronic population of the brightest excited singlet state in armchair-edge chrysene decays an order-of-magnitude faster than the one in zigzag-edge tetracene. This is correlated with a qualitatively similar difference of energy gaps between the brightest state and the state lying just below in energy, which is also consistent with our previous study on polyacenes.There is strong interest in understanding the behavior of water in its supercooled state. While many of the qualitative trends of water dynamical properties in the supercooled regime are well understood, the connections between the structure and dynamics of room temperature and supercooled water have not been fully elucidated. Here, we show that the reorientational time scales and diffusion coefficients of supercooled water can be predicted from simulations of room temperature liquid water. Specifically, the derivatives of these dynamical time scales with respect to inverse temperature are directly calculated using the fluctuation theory applied to dynamics. These derivatives are used to predict the time scales and activation energies in the supercooled regime based on the temperature dependence in one of two forms that based on the stability limit conjecture or assuming an equilibrium associated with a liquid-liquid phase transition. The results indicate that the retarded dynamics of supercooled water originate from structures and mechanisms that are present in the liquid under ambient conditions.Monolayer iron oxides grown on metal substrates have widely been used as model systems in heterogeneous catalysis. By means of ambient-pressure scanning tunneling microscopy (AP-STM), we studied the in situ oxidation and reduction of FeO(111) grown on Au(111) by oxygen (O2) and carbon monoxide (CO), respectively. Oxygen dislocation lines present on FeO islands are highly active for O2 dissociation. X-ray photoelectron spectroscopy measurements distinctly reveal the reversible oxidation and reduction of FeO islands after sequential exposure to O2 and CO. IRAK4-IN-4 price Our AP-STM results show that excess O atoms can be further incorporated on dislocation lines and react with CO, whereas the CO is not strong enough to reduce the FeO supported on Au(111) that is essential to retain the activity of oxygen dislocation lines.In this paper, we examine decay and fragmentation of core-excited and core-ionized water molecules combining quantum chemical calculations and electron-energy-resolved electron-ion coincidence spectroscopy. The experimental technique allows us to connect electronic decay from core-excited states, electronic transitions between ionic states, and dissociation of the molecular ion. To this end, we calculate the minimum energy dissociation path of the core-excited molecule and the potential energy surfaces of the molecular ion. Our measurements highlight the role of ultra-fast nuclear motion in the 1a1 -14a1 core-excited molecule in the production of fragment ions. OH+ fragments dominate for spectator Auger decay. Complete atomization after sequential fragmentation is also evident through detection of slow H+ fragments. Additional measurements of the non-resonant Auger decay of the core-ionized molecule (1a1 -1) to the lower-energy dication states show that the formation of the OH+ + H+ ion pair dominates, whereas sequential fragmentation OH+ + H+ → O + H+ + H+ is observed for transitions to higher dication states, supporting previous theoretical investigations.We present a model of a nanoscale Li-ion-type battery that includes explicit, atomistic representation of the current-carrying cations and their counter-ions. We use this model to simulate the dependence of battery performance on the transference number of the electrolyte. We report simulated values of the current at constant applied voltage for a series of model electrolytes with varying cation and anion mobilities. Unlike the predictions of macroscopic device models, our simulation results reveal that under conditions of fixed cation mobility, the performance of a nanoscale battery is not improved by increasing the transference number of the electrolyte. We attribute this model discrepancy to the ability of the electrolyte to support deviations from charge neutrality over nanometer length scales and conclude that models for nanoscale electrochemical systems need to include the possibility of deviations from electroneutrality.Even though the viscosity is one of the most fundamental properties of liquids, the connection with the atomic structure of the liquid has proven elusive. By combining inelastic neutron scattering with the electrostatic levitation technique, the time-dependent pair-distribution function (i.e., the Van Hove function) has been determined for liquid Zr80Pt20. We show that the decay time of the first peak of the Van Hove function is directly related to the Maxwell relaxation time of the liquid, which is proportional to the shear viscosity. This result demonstrates that the local dynamics for increasing or decreasing the coordination number of local clusters by one determines the viscosity at high temperature, supporting earlier predictions from molecular dynamics simulations.Hydrogenation of TiO2 enhances its visible photoabsorption, leading to efficient photocatalytic activity. However, the role of hydrogen has not been fully understood. The anatase TiO2(101) surface treated by hydrogen ion irradiation at 500 eV was investigated by photoemission spectroscopy and nuclear reaction analysis. Hydrogen irradiation induces an in-gap state 1-1.6 eV below the Fermi level and a downward band bending of 0.27 eV. The H depth profile at 300 K shows a surface peak with an H amount of (2.9 ± 0.3) × 1015 cm-2 with little concentration in a deeper region. At 200 K, on the other hand, the H depth profile shows a maximum at about 1 nm below the surface corresponding to an H amount of (6.1 ± 0.3) × 1015 cm-2 along with a broad distribution extending to 50 nm at an average concentration of 0.8 at. %. These results show that H diffusion in anatase TiO2 is much faster than in rutile TiO2 [Y. Ohashi, J. Phys. Chem. C 123, 10319-10324 (2019)]. The H diffusion coefficient at 200 K is determined to be 2.