State-to-state reaction probabilities for the H+O(2)(v,j) -> O+OH(v',j') reaction on three potential energy surfaces

We report state-to-state and total reaction probabilities for J=0 and total reaction probabilities for J=2 and 4 for the title reaction, both for ground-state and initially rovibrationally excited reactants. The results for three different potential energy surfaces are compared and contrasted. The potential energy surfaces employed are the DMBE IV surface by Pastrana [J. Phys. Chem. 94, 8073 (1990)], the surface by Troe and Ushakov (TU) [J. Chem. Phys. 115, 3621 (2001)], and the new XXZLG ab initio surface by Xu [J. Chem. Phys. 122, 244305 (2005)]. Our results show that the total reaction probabilities from both the TU and XXZLG surfaces are much smaller in magnitude for collision energies above 1.2 eV compared to the DMBE IV surface. The three surfaces also show different behavior with regards to the effect of initial state excitation. The reactivity is increased on the XXZLG and the TU surfaces and decreased on the DMBE IV surface. Vibrational and rotational product state distributions for the XXZLG and the DMBE IV surface show different behaviors for both types of distributions. Our results show that for energies above 1.25 eV the dynamics on the DMBE IV surface are not statistical. However, there is also evidence that the dynamics on the XXZLG surface are not purely statistical for energies above the onset of the first excited product vibrational state v'=1. The magnitude of the total reaction probability is decreased for J>0 for the DMBE IV and the XXZLG surfaces for ground-state reactants. However, for initially rovibrationally excited reactants, the total reaction probability does not decrease as expected for both surfaces. As a result the total cross section averaged over all Boltzmann accessible rotational states may well be larger than the cross section reported in the literature for j=1. (C) 2007 American Institute of Physics

Sodium-intercalated bulk graphdiyne as an anode material for rechargeable batteries

We present the results of a density functional theory study of sodium storage and mobility on graphdiyne (GDY) and consider the applicability of GDY intercalated with sodium (Na) as an anode material for rechargeable batteries. The maximum capacity, energy barriers for Na diffusion throughout the layers, and expansion of the layers due to Na insertion are determined. The calculations indicate that Na intercalates within the GDY bulk layers with a capacity of NaC5.14 without expansion (316 mA h g(-1)) and NaC2.57 with expansion of 28% (497 mA h g(-1)). The energy barrier for movement of Na in the slit pore formed by two GDY bulk layers is found to be 0.82 eV for bulk GDY with an AB-2 stacking, and the barrier for movement through a GDY sheet is found to be 0.12 eV. The barrier for movement in the slit pore formed by sheets becomes even lower for AB-3 stacking, with values of 0.68 and 0.40 eV found for different pathways. Movement from one GDY sheet to another for the AB-3 stacking also has a moderate energy of 037 eV. Therefore, GDY intercalated with Na is proposed to have potential as an anode material for rechargeable batteries. (C) 2017 Elsevier B.V. All rights reserved

Hydrogenated defective graphene as an anode material for sodium and calcium ion batteries: a density functional theory study

Recent experimental studies indicated that hydrogenation improves the performance of graphitic materials used as anodes in lithium and sodium ion rechargeable batteries. Here, results of density functional theory calculations are presented to demonstrate that this is also effective for both sodium and calcium ion batteries. It is shown that this can be explained by the increase in binding strength of the metal adatom to the hydrogenated graphene, compared to its binding to graphene, and also an increase in the inter-layer spacing of the layered materials. According to our calculations, whereas Na and Ca bind weakly to the graphene sheet with binding energies of −0.763 and −0.817 eV, they bind more strongly to the single layer of the proposed hydrogenated graphene sheet (CH) with binding energies of −1.670 and −2.756 eV, respectively. Furthermore, although Na does not intercalate strongly in the layers of the CH material, up to 16 Ca can intercalate into the bulk layers of this material giving an electrical capacity of 591.2 mA h/g and a 29.3% expansion of the inter-layer distance. Thus, hydrogenated defective graphene provides an anode material that might enhance the performance of rechargeable batteries compared to graphene, using metals that are cheaper than lithium

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: The dynamics on two different potential energy surfaces

The possible existence of a complex-forming pathway for the H+O2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O2(v=0,j=1)-->OH(v[prime]=1,j[prime])+O process reasonably well. ©2008 American Institute of Physic

Error bounds for the large-argument asymptotic expansions of the Hankel and Bessel functions

In this paper, we reconsider the large-argument asymptotic expansions of the Hankel, Bessel and modified Bessel functions and their derivatives. New integral representations for the remainder terms of these asymptotic expansions are found and used to obtain sharp and realistic error bounds. We also give re-expansions for these remainder terms and provide their error estimates. A detailed discussion on the sharpness of our error bounds and their relation to other results in the literature is given. The techniques used in this paper should also generalize to asymptotic expansions which arise from an application of the method of steepest descents.Comment: 32 pages, 2 figures, accepted for publication in Acta Applicandae Mathematica

B: Quantum Semiclass

Abstract. We study the transitions between the ground and excited Wannier states induced by a weak ac field. Because the upper Wannier states are several orders of magnitude less stable than the ground states, these transitions decrease the global stability of the system characterized by the rate of probability leakage or decay rate. Using non-Hermitian resonant perturbation theory we obtain an analytical expression for this induced decay rate. The analytical results are compared with exact numerical calculations of the system decay rate