Bulletin of the American Physical Society
2017 Annual Meeting of the APS Mid-Atlantic Section
Volume 62, Number 19
Friday–Sunday, November 3–5, 2017; Newark, New Jersey
Session N4: Energy Science - II |
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Chair: Mark Hybertsen, Brookhaven National Laboratory, Center for Functional Nanomaterials Room: 225, Campus Center, NJIT |
Sunday, November 5, 2017 12:15PM - 12:51PM |
N4.00001: Hidden In Plain Sight Invited Speaker: Daniel Steingart Endeavors in electrochemical energy storage are industrial masochism for the same reason they are academic hedonism: a working, rechargeable battery represents a tight coupling of multiphase phenomena across the chemical, electrical, thermal and mechanical domains. Despite these couplings, most treatments of batteries in literature emphasize the material challenges and opportunities as opposed to the system level dynamics. There good reasons for this: 1) to date, tools for examining the structure of ``real'' cells in operando are largely limited to synchrotron x-ray and neutron methods, 2) full cells are products engineered for application demands and not platonic ideals and 3) material improvements can have enormous impact on battery performance. [Preview Abstract] |
Sunday, November 5, 2017 12:51PM - 1:27PM |
N4.00002: Aqueous Semiconductor Interface Structure and Electrochemical Energy Level Alignment. Invited Speaker: Mark Hybertsen Understanding structure-function relationships at aqueous semiconductor interfaces must start from the discovery of the key interface structure motifs themselves. Important examples include the alignment of electrochemical redox levels with the semiconductor band edges and the identification of catalytic active sites. We simulate interface structure using ab initio molecular dynamics (AIMD) [1]. The degree to which interface water molecules are dissociated depends on the specific semiconductor. The proximal hydration layer structure affects the kinetic processes that control the interface equilibration. To connect the interface structure to the electrochemical redox levels, the calculated, average interface dipole is combined with the GW approach from many-body perturbation theory to calculate the energy level alignment between the semiconductor band edges and the centroid of the occupied 1b$_{\mathrm{1}}$ energy level of water and thus, the electrochemical levels [2]. The degree of interface water dissociation and the dynamical flexibility of the hydration layer both affect the level alignment. Finally, the presence of protons and hydroxyl groups at the interface affect hole localization. Results will be discussed for GaN, ZnO, and both rutile and anatase forms of TiO$_{\mathrm{2}}$. [1] N. Kharche, et al., \textit{Phys. Chem. Chem. Phys.} 16, 12057 (2014). [2] N. Kharche, et al., \textit{Phys. Rev. Lett.} 113, 176802 (2014). [Preview Abstract] |
Sunday, November 5, 2017 1:27PM - 1:39PM |
N4.00003: Statistics of nucleation in small and large systems Vitaly Shneidman Statistics of single- and multiple nucleation events in systems of variable sizes is considered in the context of large scale simulations. The earlier obtained singular perturbation solution of the time-dependent Becker-D\"oring equation is used to predict the probability distribution of the waiting times to detect the first nucleus in a small system and to establish connection with the number of nuclei when the system is large. Examples include dynamic Monte Carlo simulations of condensation of a supersaturated lattice gas \footnote{V.A. Shneidman \textbf{ J. Chem. Phys.} 141 (2014) 051101.}, where exact results for the nucleation rates obtained from low-temperature cluster expansions \footnote{V.A. Shneidman and G.M. Nita, \textbf{ Phys. Rev. Lett.} 97 (2006) 065703.} provide a rigorous independent test. Stochastic (Langevin) simulations \footnote{V.A. Shneidman \textbf{ J. Chem. Phys.} 147 (2017) 061101.} of the evolution of a bubble in viscous and inertial fluid, discussed in the context of the cavitation problem \footnote{V.A. Shneidman \textbf{Phys. Rev. E} 94 (2016) 062101. } also are considered. [Preview Abstract] |
Sunday, November 5, 2017 1:39PM - 1:51PM |
N4.00004: Electron Transfer rate calculation for electrodes with immobilized enzymes on Carbon Nanotubes Ashvin Kumar Vasudevan, Gordon.A Thomas, Reginald.C Farrow, Alokik.P Kanwal, Shachi Yadav Fuel Cells are rapidly emerging as an alternate fuel source to produce power at a high efficiency. Enzymatic fuel cells provide a way to use cheap fuels while eliminating the use of metals. While the cost of the fuel cell is usually cheap, problems arise due to inefficient electron transfer from the enzyme to electrode. Our group addresses this by incorporating vertically aligned carbon nanotubes (enzymes immobilized onto them) to help promote the electron transfer. This talk deals with the theoretical calculations involved in the process. To obtain an accurate prediction of the electron transfer, the environment, the orientation of the enzyme on the electrode, distances involved in the electron transfer, type of reaction and the energies of the enzymes involved before and after the electron transfer are to be considered. The calculation follows Marcus' theory with the enzymes used, Glucose oxidase and laccase, taken as donor and acceptor. Hence to solve the electron transfer equation, the free energies, reorganization energies -- inner shell and the outer shell must be found. These energies were obtained with the help of the x-ray structures found in the protein database. The parameters involved in each calculation will be reviewed. [Preview Abstract] |
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