Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session B3: TM First Principles Methods I |
Hide Abstracts |
Chair: Marc Cawkwell, Los Alamos National Laboratory Room: Fifth Avenue |
Monday, July 8, 2013 9:15AM - 9:45AM |
B3.00001: ABSTRACT WITHDRAWN |
Monday, July 8, 2013 9:45AM - 10:00AM |
B3.00002: Predicting Variable Stoichiometric Compounds under High Pressure Qiang Zhu, Artem Oganov Materials under pressure often exhibit exotic physical and chemical behaviors. In particular, extremely new stable compounds appear. Here, we studied the variation of stoichiometry under pressure by using the evolutionary search scheme. Two kinds of oxides (Xe-O and Mg-O) have been investigated under megabar pressures. For XeO, we predict the existence of thermodynamically stable Xe-O compounds at high pressures (XeO, XeO2 and XeO3 become stable at pressures of 83, 102 and 114 GPa, respectively). For Mg-O, our calculations find that two extraordinary compounds MgO2 and Mg3O2 become thermodynamically stable at 116 GPa and 500 GPa, respectively. Our calculations indicate large charge transfer in these oxides for both systems, suggesting that large electronegativity difference and pressure are the key factors favoring their formations. We also discuss if these oxides might exist at earth and planetary conditions. [Preview Abstract] |
Monday, July 8, 2013 10:00AM - 10:15AM |
B3.00003: Tuning dimensionality in binary Li-B compounds and evaluating thermodynamic vs kinetic stability under pressure Andreas Hermann The binary phase diagram of the light elements lithium and boron features an intriguing phase with a finite range of stability, LiB$_{\mathrm{x}}$ with 0.8$\le $x$\le $1.0. The experimental hexagonal structure contains two incommensurate sub-lattices, a hexagonal lithium network, and an array of linear boron chains. An alternative structure of almost equal energy is inspired by the AlB$_{\mathrm{2}}$ structure type, and contains graphitic boron sheets interspersed by trigonal lithium layers. We present results from a computational study on this system, at atmospheric and elevated pressures. We model the tunable atomic composition and predict the disappearance of the finite stability range of LiB$_{\mathrm{x}}$ at P$=$40GPa, where layered structures become more stable than chain-like structures across the entire composition range. Kinetic barriers are estimated and are predicted to facilitate the recovery of phases synthesized at high pressure. Up to P$=$70GPa, all stable structures are metallic, and trends of their electronic and dynamic properties will be discussed. At P\textgreater 70GPa, structure searches reveal that stoichiometric 1:1-LiB is most stable in the NaTl structure, with a diamondoid boron network, and becomes an insulator. The Zintl-Klemm concept helps understand the different structural choices under pressure. [Preview Abstract] |
Monday, July 8, 2013 10:15AM - 10:30AM |
B3.00004: Monitoring bonding reconstruction across the $\alpha$-cristobalite $\rightarrow$ stishovite phase transition in silica \'Angel Morales Garc\'Ia, Miguel A. Salvad\'o, Pilar Pertierra, J.M. Men\'endez, J.M. Recio We propose a microscopic mechanism that describes how the structure and bonding network of $\alpha$-critobalite transforms into stishovite at constant pressure and temperature. A martensitic-like approach that preserves the traslational symmetry is used to modelize the simultaneous and coordinated movement of all the atoms as the transition progresses. Relevant distances and angles, cell strains, and atomic displacements across the transition path are obtained from first-principles calculations under the generalized gradient approximation of the density functional theory. A soft and symmetric energetic profile is computed with an activation barrier lower than 100 kJ/mol at the thermodynamic transition presure. Thanks to the analysis of the calculated topology of the electron localization function, we are able to provide visual and quantitative information on the chemical bonding reorganization that accompanies this transformation, mainly the increasing of Si and O coordinations from 4-fold to 6-fold and from 2-fold to 3-fold, respectively. We do not detect any bond breaking, but the formation of two new Si-O chemical bonds involving oxygen atoms from the third coordination sphere of Si. It is not until the Si-O distance is close to 2.0 \AA ~ when the new bonds emerge. [Preview Abstract] |
Monday, July 8, 2013 10:30AM - 10:45AM |
B3.00005: Stability of Solid Oxygen at High Pressure Sabri Elatresh, Stanimir Bonev Despite extensive theoretical and experimental studies, the stability of solid oxygen at high pressure remains an open question. Recent experimental results proposed a new phase that is stable at finite temperature [1]; however, the evidence is not conclusive. In this work, we reexamine the stability of the phase diagram of solid oxygen up to 100 GPa. In particular, we focus on the mechanical and thermodynamic stability of the recently proposed finite temperature phase. The influence of exchange interactions and the role of ion dynamics, including quantum effects, will be discussed.\\[4pt] [1] Alexander F. Goncharov, et al. \textbf{135}, 084512 (2011). [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