Bulletin of the American Physical Society
2020 Annual Meeting of the APS Four Corners Section (Virtual)
Volume 65, Number 16
Friday–Saturday, October 23–24, 2020; Albuquerque, NM (Virtual)
Session B06: Materials ILive
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Chair: John Harton, CSU |
Friday, October 23, 2020 10:30AM - 10:42AM Live |
B06.00001: MATCOR, a Program for the Cross-Validation of Material Properties Between Databases. JORGE MARQUEZ CHAVEZ, Boris Kiefer Many technological materials are currently improved using data analytics and Machine Learning methods. In this effort it is clear that the fidelity of the input data can affect the reliability of the model predictions. In our contribution we focus on the input data and their consistency between materials databases. We developed MATCOR, an open-source software to facilitate the initial data verification. MATCOR verifies material properties between AFLOW and Materials Project through materials chemistry and crystallography, as well as computational parameters. The capabilities of MATCOR are demonstrated for several examples. Density shows the highest correlation among the tested properties, 98{\%} of the materials agree to within \textpm 2.6{\%}. Bulk- and shear-moduli showed deviations of less than \textpm 10{\%} for 79.4{\%} and 65.1{\%} of the materials, respectively. The classification in materials as non-magnetic/paramagnetic and metallic/gapped are consistent among the two databases for 91{\%} and 73{\%} of the materials, respectively. These examples show that MATCOR can be used to accelerate data curation and outlier identification, crucial prerequisites for model building and materials discovery. [Preview Abstract] |
Friday, October 23, 2020 10:42AM - 10:54AM Live |
B06.00002: An Information Geometry Approach to Uncertainty Quantification of Sloppy Interatomic Models Cody Petrie, Yonatan Kurniawan, Kinamo Williams, Mark Transtrum Atomistic simulations often use fitted Interatomic Models (IMs) due to their ability to quickly compute the energy and forces on collections of atoms. Estimating the uncertainty in the fitted parameters is important for assessing the reliability of a model's predictions. Multiparameter models, including many IMs, are often sloppy, i.e., exhibit an extreme insensitivity to coordinated changes in some of their parameter values. Consequently, fitted parameters often have large uncertainties and quantifying this uncertainty can be challenging when models are sloppy. We use an information geometry approach to systematically explore the parameter space of families of IMs, identifying regions of sloppiness. In this approach, a multiparameter model is interpreted as a manifold of potential predictions with parameters as coordinates. We numerically calculate geodesics on the model manifold and identify boundaries of the manifold that are associated with coordinated, extreme values of the parameters. We show how these boundaries are related to sloppiness and uncertainty in fitted parameter values and discuss implications for model selection and uncertainty quantification in atomistic simulations. [Preview Abstract] |
Friday, October 23, 2020 10:54AM - 11:06AM Live |
B06.00003: Anisotropic domains and antiferrodistortive-transition controlled magnetization in epitaxial manganite films on vicinal SrTiO$_{\mathrm{3}}$~substrates Binod Paudel, Bruce Zhang, Yogesh Sharma, Kyeong Tae Kang, Heinrich Nakotte, Haiyan Wang, Aiping Chen We studied the microstructural evolution and magnetism of ferroelastic La$_{\mathrm{0.9}}$Sr$_{\mathrm{0.1}}$MnO$_{\mathrm{3}}$~(LSMO) epitaxial thin films grown on SrTiO$_{\mathrm{3}}$~(001) substrates with different miscut angles. The substrate miscut angle plays a critical role in controlling the in-plane magnetic anisotropy. The microscopic origin of such magnetic anisotropy is attributed to the formation of anisotropic stripe domains along the surface step terraces. The magnetization in the LSMO films was found to be selectively modulated by the antiferrodistortive phase transition of the SrTiO$_{\mathrm{3}}$~substrate. This phenomenon has been qualitatively explained by a strain modified Stoner--Wohlfarth model. We conclude that the magnetization modulation by the SrTiO$_{\mathrm{3}}$~phase transition depends on~$h$, the ratio of applied magnetic field to the saturation field. Such modulation is only visible with~$h$?\textless ?1. The established domain microstructure--anisotropy--magnetism correlation in manganite films can be applied to a variety of complex oxide thin films on vicinal substrates. [Preview Abstract] |
Friday, October 23, 2020 11:06AM - 11:18AM Live |
B06.00004: Space Environment Degradation of LDEF Thermal Control Paints Trace Taylor, Ben Bradshaw, JR Dennison Space environmental degradation of Long Duration Exposure Facility (LDEF) white thermal control coatings was studied. Prolonged exposure modified properties of these spacecraft materials, such as optical reflectivity and emissivity, which regulate satellite thermal control and electron emission and conductivity which determine spacecraft charging and electrostatic discharge. Tests of 1980s vintage LDEF samples are still relevant, as few long-exposed materials are available for study due to the expense of their launch and retrieval. LDEF panels coated with white A276 TiO$_{\mathrm{2}}$ epoxy-based paint turned, in varying degrees, to yellow or dull brown and showed up to \textasciitilde 2X increase in electron emission. Changes were likely due to UV and atomic oxygen degradation of the epoxy or contamination from outgassing of adjacent materials. Electron emission and optical reflectivity are both affected by surface roughness, oxidation, chemical decomposition, and contamination, all of which evolved for these LDEF samples subjected to electron, ion, and photon radiation, atomic oxygen, and small orbital debris for 69 months. To better understand the nature, composition, and sources of degradation and contamination, measurements of exposed panels, flight control samples, and potential outgassing sources were compared, including: electron yields; scanning electron microscopy and energy-dispersive x-ray spectroscopy; diffuse/specular UV-Vis-NIR reflectivity; and Fourier transform IR spectroscopy. [Preview Abstract] |
Friday, October 23, 2020 11:18AM - 11:30AM Live |
B06.00005: Energetic Distribution of States in Irradiated Low-Density Polyethylene from UV-Vis-NIR Spectroscopy Zachary Gibson, Benjamin Bradshaw, JR Dennison, Elena Plis, Daniel Engelhart, Ryan Hoffmann Optical spectroscopy has been used to characterize the energetic density of states of low-density polyethylene (LDPE) and determine its optical band gap, E$_{\mathrm{g}}$, and Urbach Energy, E$_{\mathrm{U}}$ (a measure of the width of the energetic distribution of localized states within the mobility gap of disordered materials). LDPE is a prototypical highly disordered insulating material; its properties are of practical interest due to its myriad of applications from spacecraft charging to high voltage DC power cable insulation, where it can be susceptible to ionizing and UV radiation. To determine the effects of radiation on the density of states, UV-Vis-NIR transmittance spectra (200-2500 nm wavelength) were measured for pristine and irradiated samples. Total ionizing doses of 1 MGy and 4 MGy from a monoenergetic 100 keV electron beam were studied. To more accurately determine the absorption coefficient (and therefore E$_{\mathrm{U}})$, the reflectance is also required. Reflectance and transmittance were measured for pristine LDPE and these data were then used to scale the measurements of the irradiated samples. Comparison with other methods to determine the energy density of states of LDPE are discussed. [Preview Abstract] |
Friday, October 23, 2020 11:30AM - 11:42AM |
B06.00006: Corrosion resistant magnesium alloy design based on the First-principles calculation. Yaowei Wang, Tian Xie, Xiaoqin Zeng, Hong Zhu Second phase strengthening has been widely used in alloys designs, many of which however have been reported to enhance the galvanic corrosion of magnesium alloys. However, up to now, a repeatable method to predict corrosion current density and potential still needs to be explored. In this study, a semi-empirical model was proposed based on the mixed potential theory and first principles calculation to analyze the galvanic corrosion of the alloys. Our model is further validated in the case of Mg-Ge alloys, which is composed of anode Mg matrix and cathode Mg2Ge second phase. The estimated exchange current of the hydrogen evolution upon Mg2Ge is about 3 orders of magnitude smaller than that on pure Mg, indicating the depressed galvanic corrosion of the Mg-Ge alloys is the simultaneous result of the low hydrogen exchange current upon Mg2Ge. Moreover, some typical intermetallics, such as MgZn2 and MgSc, were selected to compare the different corrosion properties of the alloys, which is in close agreement with the experimental observations. Our model is capable of predicting the galvanic corrosion behavior and provide a promising perspective for designing better corrosion-resistant alloys. [Preview Abstract] |
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