Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K25: Journal of Chemical Physics Editors' ChoiceInvited
|
Hide Abstracts |
Sponsoring Units: DCP Chair: Scott Anderson, Univ of Utah Room: LACC 403B |
Wednesday, March 7, 2018 8:00AM - 8:36AM |
K25.00001: Mass Density Fluctuations in Quantum and Classical Descriptions of Liquid Water Invited Speaker: Gregory Schenter Establishing a self-consistent simulation protocol for first principles statistical mechanics using advanced density functional theory electronic structure is essential. We demonstrate this by studying the properties of the water liquid/vapor interface and its impact on concepts of solvation and hydrophobicity. Our challenge is to unravel the relation between properties and structures and fluctuations of the system. This will lead to an improved understanding of the relation between details of molecular interaction and collective phenomena. |
Wednesday, March 7, 2018 8:36AM - 9:12AM |
K25.00002: Photocatalysis on metal oxides: insights from simulations Invited Speaker: Annabella Selloni Semiconductor-based photocatalysis for the degradation of pollutants and the splitting of water into H2 and O2 has been an important area of research for decades. In this talk I present recent applications of first principles electronic structure calculations and molecular dynamics simulations to understand materials properties and reaction mechanisms on metal oxide photocatalysts. I shall focus mainly on anatase TiO2, an oxide semiconductor that is widely used in photocatalysis and solar energy conversion. Examples include the structure and reactivity of anatase TiO2 surfaces and aqueous interfaces, the behavior of charge carriers at these interfaces, and the formation and structure of so-called black TiO2, a modified TiO2 material capable to absorb the whole spectrum of visible light. |
Wednesday, March 7, 2018 9:12AM - 9:48AM |
K25.00003: Reversed interfacial fractionation of carbonate and bicarbonate evidenced by X-ray photoemission spectroscopy Invited Speaker: Hendrik Bluhm The fractionation of ions at liquid interfaces and its effects on the interfacial structure are of vital importance in many scientific fields. Of particular interest is the aqueous carbonate system, which governs both the terrestrial carbon cycle and physiological respiration systems. We have investigated the relative fractionation of carbonate, bicarbonate, and carbonic acid at the liquid/vapor interface finding that both carbonate (CO32- ) and carbonic acid (H2CO3) are present in higher concentrations than bicarbonate (HCO3- ) in the interfacial region. While the interfacial enhancement of a neutral acid relative to a charged ion is expected, the enhancement of doubly charged, strongly hydrated carbonate anion over the singly charged, less strongly hydrated bicarbonate ion is surprising. As vibrational sum frequency generation experiments have concluded that both carbonate and bicarbonate anions are largely excluded from the air/water interface, the present results suggest that there exists a significant accumulation of carbonate below the depletion region outside of the area probed by sum frequency generation. |
Wednesday, March 7, 2018 9:48AM - 10:24AM |
K25.00004: IR spectral assignments for the hydrated excess proton in liquid waterIR spectral assignments for the hydrated excess proton in liquid water Invited Speaker: Gregory Voth The local environmental sensitivity of infrared (IR) spectroscopy to hydrogen-bonding structure makes it a powerful tool for investigating the structure and dynamics of excess protons in water. Although of significant interest, the line broadening that results from ultrafast evolution of different solvated proton–water structures makes assignment of liquid-phase IR spectra a challenging task. In this work, we apply a normal mode analysis using density functional theory to thousands of proton–water clusters taken from reactive molecular dynamics (MD) trajectories of the latest generation multistate empirical valence bond proton model (MS-EVB 3.2). These calculations are used to obtain a vibrational density of states and IR spectral density, which are decomposed on the basis of solvated proton structure and the frequency dependent mode character. Decompositions are presented on the basis of the proton sharing parameter δ often used to distinguish Eigen and Zundel species, the stretch and bend character of the modes, the mode delocalization, and the vibrational mode symmetry. We find that there is a wide distribution of vibrational frequencies spanning 1200-3000 cm-1 for every local proton configuration, with the region |
Wednesday, March 7, 2018 10:24AM - 11:00AM |
K25.00005: Advances in nanoparticle structure characterization by X-ray absorption spectroscopy Invited Speaker: Anatoly Frenkel X-ray absorption fine structure (XAFS) spectroscopy has been used to study short range order in nanoparticles for four decades. Due to their role in catalysis, we briefly revisit their structural and compositional descriptors that affect their reactivity. Among the most frequently used descriptors are various attributes of structure, shape and compositional motifs (e.g., core-shell, random or cluster-by cluster). This talk will review new methods of data analysis and modeling of nm-scale nanoparticles and sub-nm clusters that extend beyond conventional fitting of experimental XAFS spectra. One recent method, based on parameter-free MD simulations, was validated on the example of Pd-Au nanoalloys containing about 100 atoms with narrow size and compositional distributions, where random mixing of Pd and Au atoms was demonstrated earlier by conventional Extended XAFS (EXAFS) analysis.1 New Machine Learning approaches for “on the fly” analysis of X-ray Absorption Near Edge Structure (XANES) spectroscopy in ultra-small clusters will be presented for mono- and bimetallic alloys that are often investigated in operando conditions. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700