Bulletin of the American Physical Society
2007 APS Four Corners Section/SPS Zone 16 Joint Fall Meeting
Volume 52, Number 14
Friday–Saturday, October 19–20, 2007; Flagstaff, Arizona
Session C2: Metals |
Hide Abstracts |
Chair: Gus Hart, Brigham Young University Room: Chemistry (Bldg. 20) Room 225 |
Friday, October 19, 2007 3:25PM - 4:01PM |
C2.00001: Helium in metals: interesting science in the national interest Invited Speaker: Many rare-earth and transition metals readily react with hydrogen to form distinct metal-hydrogen phases. While the hydrogen density of the rare-earth and transition metal hydrides is very high, their hydrogen mass density is very low. The low mass density makes them not suitable for use in automobile on-board hydrogen storage but they are excellent for long term hydrogen storage in situations where weight is not a factor. At Sandia National Laboratories, we are interested in storing the hydrogen isotope tritium. Tritium is interesting because it is radioactive, decaying into $^{3}$He with a half-life of 12.3 years. Helium is insoluble in metals and forms highly pressurized helium bubbles in the metal lattice while only a small fraction of the generated helium escapes from the metal. In this presentation I will share some of the interesting physics and chemistry that we have discovered about metal tritides and helium in metals. [Preview Abstract] |
Friday, October 19, 2007 4:01PM - 4:13PM |
C2.00002: How does a crystal melt? Sheng-Nian Luo, Qi An, Lianqing Zheng Melting is one of the most important yet poorly understood phenomena. Nucleation and growth of melt play a key role in melting processes, and occur at sub-ns and sub-ns scales which essentially preclude direct observation of the initial stages of melting. Inherent defects also complicates the whole process. An indispensable first step is to understand the melting of an initially defect and surface free solid, namely, homogeneous nucleation. A natural tool to decipher the physics of melting is molecular dynamics simulations on a simple system. We have conducted such simulations on Cu described by an accurate embedded atom method potential on system sizes ranging from $10^3$ to $10^6$ atoms. The structural evolution of the system is characterized with local and global order parameters, and the evolution of liquid, with cluster analysis. The size distribution of liquid nuclei is thus quantified for a single run. As fluctuations are ubiquitous and critical for phase transitions, we adopt the mean first passage time method to obtain statistically from 100 MD runs the critical nucleus size, Zeldovich factor and steady state nucleation rate. The nucleation and growth of melt, with the aid of fluctuations, are demonstrated by the simulations; classical nucleation theory can describe the nucleation process with reasonable accuracy, if the solid$-$liquid interface is properly considered. We also present shock wave induced melting of Cu single crystals. [Preview Abstract] |
Friday, October 19, 2007 4:13PM - 4:25PM |
C2.00003: Interfacial Core-Level Shifts at W(110)-Based Bimetallic Interfaces D. Mark Riffe Due to their unique chemical, electronic, and magnetic properties, bimetallic epitaxial systems continue to receive a great deal of attention. A unique probe of these interfaces is core-level photoemission spectroscopy: by measuring shifts in core-level binding energies for interfacial atoms (compared to atoms in the bulk solid), qualitative information about atom-specific electronic structure can be inferred. In addition to this qualitative information, the interfacial binding-energy shifts have a thermodynamic interpretation that provides quantitative information about inter-metallic solution energies. Here we discuss W $4f_{7/2}$ core-level binding-energy shifts of the first layer of W(110) for a number of W(110)-M bimetallic layers, where M includes Na, K, Cs, Ba, Cr, Mn, Fe, Ni, Pd, Ag, Pt, and Au. Overall, the W interfacial core-level shifts correlate well with the difference in solution energies of Re in M and W in M [A. R. Miedema \emph{et. al}, CALPHAD \textbf{1}, 341 (1977)], in agreement with the partial-shift theory of Nilsson \emph{et. al} [Phys. Rev. B \textbf{38}, 10357 (1988)]. [Preview Abstract] |
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