Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session C04: Computational Physics 1 |
Hide Abstracts |
Chair: Stacy Copp, Los Alamos National Lab Room: CSC 10/12 |
Friday, October 12, 2018 10:45AM - 11:09AM |
C04.00001: Predicting shock-initiated detonation in nanoporous energetic materials. Invited Speaker: Ryan R Wixom Since the invention of dynamite, we have empirically understood that microstructure governs how easily an explosive can be persuaded to release its chemical energy. But if we could more precisely predict the sensitivity of energetic materials, we could also optimize formulations for safe and reliable performance. Consequently, we present a mesoscale hydrodynamic simulation of a thin flyer-plate impacting a nanoporous explosive. The resulting short-pulse shock wave is concentrated by pores, where high pressures and temperatures initiate chemical reactions that build into a detonation. This simulation is the culmination of three related research efforts: characterization of nanoscale heterogeneities using ion-beam and electron microscopy, equation of state development using density functional theory, and parameterization of reaction models via small-scale photonic Doppler velocimetry experiments. We discuss the integration of these efforts and draw comparisons between the simulation and experimental data to explore future prospects for using simulations to predict safety, aid design, and tailor materials for optimal performance. |
Friday, October 12, 2018 11:09AM - 11:21AM |
C04.00002: Dependence of the superconducting superheating field on material inhomogeneity Jared Carlson, Mark Transtrum, Alden R Pack In particle accelerators, Superconducting Radio Frequency (SRF) cavities are used to transfer energy to particles through induced electric fields. A limiting factor in the efficiency of these cavities is the superconducting material’s properties, mainly the so-called superheating field, i.e., the largest magnetic field that the superconductor can withstand before becoming a normal metal. Using the Ginzburg-Landau model, we explore the dependence of the superheating field on the type and purity of the superconducting materials used. We solve the Ginzburg-Landau equations using finite element numerical methods. Our goal is to understand the role of material inhomogeneity, such as those found at grain boundaries, in determining a sample's superheating field. Our results will allow for more effective SRF cavities to be constructed, which will decrease both the cost and size of particle accelerators. |
Friday, October 12, 2018 11:21AM - 11:33AM |
C04.00003: Algorithms for Inferring the Information Topology of Statistical Mechanics Models Mark Transtrum, Alexander J Shumway, Kolten Barfuss Multi-parameter models of complex systems are ubiquitous throughout science. We interpret models geometrically as manifolds with parameters as coordinates. For many models, the manifold is bounded with a hierarchy of boundaries. These boundaries are themselves manifolds which correspond to simpler models with fewer parameters. The hierarchical structure of the boundaries induces a partial order relationship among these approximate models that can be visually represented in a Hasse diagram. The Hasse diagram of the model manifold provides a global summary of the model structure and a road map from the intricate, fully parameterized description of a complex system through various types of approximations to the set of distinct behavior regimes the model enables. I describe a method for reconstructing the entire Hasse diagram and discuss applications to models in statistical mechanics. |
Friday, October 12, 2018 11:33AM - 11:45AM |
C04.00004: Water Binding Geometries in Complex Oxides as Determined by Rotational Equilibrium. Seyedayat Ghazisaeed, Jakub Plášil, Boris Kiefer Water binding geometry can have a significant effect on the stability of materials and their performance. The experimental determination of H_{2}O orientation in crystals is challenging due to the small x-ray scattering cross section of low-Z elements such as hydrogen. We have shown previously that rotational equilibrium constraints can successfully overcome experimental limitations for identifying water orientations in ionic crystals. In order to avoid singularities in energy the crystal should be charge neutral. However, this can be unexpectedly challenging in the presence of partial occupancies, a situation that is often encountered in real materials. Here we explore the effect how charge neutrality violation affects predicted H_{2}O orientations. Pb-uranyl-oxide, curite (H10, O32, Pb2.894, U8), is chosen as an example where the structure could not be completely resolved from x-ray experiments. We tested several crystallographic approaches to select charges with and without charge neutrality constraint and found that ~80% of the 10000 calculated initial configurations, for 20 different charge models converged to a single final H_{2}O configuration. This strongly suggests that the rotational equilibrium method can be used successfully in cases where charge neutrality violation occur. |
Friday, October 12, 2018 11:45AM - 11:57AM |
C04.00005: Identifiability Analysis of a Simplified Combustion Model Adam Fletcher, Mark Transtrum Combustion is essential in modern society. It is the underlying process that powers much of our transportation and enables the creation of many goods we use on a regular basis. However, it is a difficult process to model. It involves many chemical species that are in turn involved in a complex network of chemical reactions. Models of this process include a large number of unknown parameters that need to be estimated from data. For example, we consider a “simplified” model involving nine species that has 231 unknown parameters. Because most of these parameters are irrelevant, we seek a simplified effective description of the combustion process. As a preliminary calculation we perform an identifiability analysis on this model. Our approach is to calculate the sensitivity of the model’s predictions to variations in the parameter values. I report on which types of parameters are identifiable in this model and the chemical insights this analysis provides. |
Friday, October 12, 2018 11:57AM - 12:09PM |
C04.00006: Discovery of New Materials: why we care and how we are doing it Natalie L Coy, Jeremy Jorgensen, Gus L.W. Hart Discovery of new materials---from plastics, electronics, synthetic fabrics, and metal alloys---has a tremendous impact on our quality of life. The number of possible new materials to explore is immense, numbering in the trillions at least. Materials scientists explore these possibilities experimentally and computationally, but both approaches would require billions of years to try all possibilities. Our goal is to speed up such simulations. One of the key challenges is to accelerate the numerical integral for computing the band energy. Knowing band energy is essential to compute the stability of a candidate material. The numerical integral for band energy converges slowly (high accuracies require a dense integration mesh). In order to speed up the convergence, we integrate the bands analytically using a high-order polynomial interpolation method. We will discuss results for a 2D toy problem that illustrates our approach. |
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. |
© 2021 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
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700