Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session R43: Computational Design and Discovery of Novel Materials IIIFocus
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Sponsoring Units: DCOMP DMP Chair: Cai-Zhuang Wang, Ames Laboratory Room: 702 |
Thursday, March 5, 2020 8:00AM - 8:36AM |
R43.00001: Creating Novel Magnetic Compounds with Complementary Experimental and Computational Methods Invited Speaker: David Sellmyer New materials discovery has governed the development of science and technology for decades. In particular, the search for new magnetic compounds is important to satisfy ever-increasing demand for magnets with a wide range of applications including spintronics, data storage, hybrid vehicles, and wind turbines. This requires efficient computational and experimental approaches for high throughput and efficiency [1]. When increasingly powerful computational techniques are combined with special fabrication methods far from equilibrium, the search also can uncover new metastable magnetic compounds [2-6]. This talk will focus on the development of novel magnetic compounds with high magnetocrystalline anisotropy, magnetization, and Curie temperature by combining experiments, an adaptive genetic algorithm search, and electronic-structure calculations. Magnetism of novel compounds such as Fe3+xCo3-xTi2, Co3N, Fe2CoC, and Co3Si will be discussed in terms of intrinsic atomic-scale and extrinsic nanoscale effects. This research is done in collaboration with D.J. Sellmyer, C.Z. Wang, K.M. Ho, X. Xu, and J. R. Chelikowsky. |
Thursday, March 5, 2020 8:36AM - 8:48AM |
R43.00002: A high throughput workflow for magnetic ferroelectrics from first-principles Stephanie Mack, Tess E Smidt, Sinéad Griffin, Jeffrey B Neaton Multiferroics, which combine ferroelectricity and magnetism, are of great interest for a variety of electronics applications. Although discovery of new multiferroics based on chemically manipulating known structural motifs has yielded new candidates, there are still relatively few known multiferroics with highly tunable electric and magnetic orders at room temperature. Using symmetry constraints based on Landau theory of phase transitions, and on the identification of both a polar and nonpolar reference structure, and first-principles density functional theory calculations using the Materials Project database, we develop a high throughput workflow to predict the ground state magnetic ordering and spontaneous polarization of new multiferroic candidate materials. Comparison to known multiferroics will be discussed, and we will classify the most promising candidate materials to aid future synthesis efforts. This work is supported by the Department of Energy through the Materials Project FWP at Berkeley Lab. Computational resources provided by NERSC. |
Thursday, March 5, 2020 8:48AM - 9:00AM |
R43.00003: Generating a database of predicted ground-state magnetic orderings of inorganic crystalline materials suitable for high-throughput screening applications Matthew Horton, Kristin Persson Bridging the gap from toy model to synthesizable material and ultimately to working device is of crucial importance when investigating exotic magnetic phenomena. Since 2011, The Materials Project has offered an open-access database of inorganic crystalline materials and their associated properties as calculated by Density Functional Theory. However, to date, the magnetic ordering of these materials has not been explored in a systematic way. |
Thursday, March 5, 2020 9:00AM - 9:12AM |
R43.00004: Machine-learning Assisted Prediction of Magnetic Double Perovskites Tanusri Saha-Dasgupta, Anita Halder, Aishwaryo Ghosh In the present study, we use a combination of computational tools; machine learning technique for screening of stable candidates, evolutionary algorithm for crystal structure determination, and first-principles calculations for characterization of |
Thursday, March 5, 2020 9:12AM - 9:48AM |
R43.00005: First-principles design of solid-state hydrogen electrolytes Invited Speaker: Andrew Rowberg Defects and impurities play an important role in determining the properties of materials and must be carefully considered as part of materials design and synthesis. This applies to semiconductors and materials used for energy generation and storage. Defects can act as electron donors or acceptors, implying that their concentrations can be tuned by introducing oppositely charged species. These dopants must be carefully chosen to avoid undesirable side effects, such as autocompensation or, in the case of ionic conductors, high mobile carrier binding energies. |
Thursday, March 5, 2020 9:48AM - 10:00AM |
R43.00006: Atomistic Kinematics of Carbon Diffusion and Clustering in BCC Fe with Point Defects Tien Quang Nguyen, Kazunori Sato, Yoji Shibutani Carbon diffusion and clustering in iron are important phenomena as they closely link to processes of production of steels such as cementite formation, phase transition, and so on. Here, we studied these phenomena using multi-scale approach. First, the stability of carbon and its interaction with point defect were examined via total energy optimization using our own newly developed Fe-C potential. Then, the diffusion mechanisms for carbon interstitials were analyzed. By using kinetic Monte Carlo (kMC) simulations, diffusion coefficients of carbon depending on temperature were estimated to clarify the influence of vacancy on the diffusion and clustering processes. We found that in perfect lattice, carbon atoms tend to form stable C-C pairs, while the presence of vacancies leads to the formation of larger vacancy-carbon (VCn) clusters with VC2 as the most stable structure. In addition, due to the presence of vacancies, the diffusion paths of carbon are strongly modified. The kMC simulations show that diffusion coefficient is decreased as vacancy content increases. Therefore, it is suggested that vacancies may play an important role in the clustering process of carbon. |
Thursday, March 5, 2020 10:00AM - 10:12AM |
R43.00007: First-principles Study of Large Seebeck Coefficients in Fe-doped Si-Ge Alloys Ryo Yamada, Akira Masago, Tetsuya Fukushima, Hikari Shinya, Tien Quang Nguyen, Kazunori Sato Si-Ge alloys are one of the cheapest nontoxic thermoelectric materials utilized at high temperatures, but their dimensionless figure of merit, ZT, is relatively small. To improve their low ZT values, there are some attempts to modify an electronic band structure by doping Fe, and it has been reported that a high ZT value, ZT>1.88 (at T=873K), as well as a large Seebeck coefficient, |S|>517μV/K (at T=673K), were produced in the nanostructured Si0.55Ge0.35P0.10Fe0.01 sample [1]. It is believed that they originate from a strong peak at the edge of the conduction band generated by the Fe-doping (a so-called impurity state). However, an occurerence of the impurity state in the Fe-doped Si-Ge system has not been confirmed yet. In this work, therefore, the impurity state in the Fe-doped Si-Ge alloys is calculated from an electronic band structure calculation, and the reported large Seebeck coefficient is reproduced with the use of the linear response theory. Using a special quasi-random structure with a hybrid functional (HSE06), the impurity state was successfully produced, and computed Seebeck coefficients showed good agreement with the experimental data. |
Thursday, March 5, 2020 10:12AM - 10:24AM |
R43.00008: Assessing Aqueous Stability of Nonequilibrium Nickel Chromium Oxides from First Principles Kathleen Mullin, Michael Waters, James Rondinelli Ni-Cr alloys are used in high tempurature applications where corrosion resistance is critical to performance. It has generally been thought that this corrosion resistance comes from a passive film made of NiO with the rock salt crystal structure and Cr2O3 with the corundum crystal structure. Recently, however, new data shows that valence-precise compositions and bulk equilibrium structures do not necessarily form in the ultrathin limit[1]. Specifically, Ni-Cr alloys form nonequilibrium phases through a solute capture process, whereby Ni-Cr oxide in the rock salt structure with unexpectedly large solubility of Cr on the Ni lattice occurs (and likewise for Ni in the corundum lattice). In order to better understand the formation of this nonequilibrium oxide, we use ab-initio Density Function Theory calculations to parameterize a cluster expansion model of the Ni-Cr-O system as a function of Cr and Ni content. Next, we use energies of formation derived from the cluster-expansion for use in electrochemical Pourbaix diagrams to understand the impact of the nonequilibium compositions on the stability of the oxide in aqueous environments. |
Thursday, March 5, 2020 10:24AM - 10:36AM |
R43.00009: Influence of cation site disorder in ZnGeN2 on electronic properties Jacob Cordell, Jie Pan, Celeste Melamed, Garritt Tucker, Adele Tamboli, Stephan Lany Cation disorder-dependent II-IV-V2 materials show promise for tuning band gaps with lattice parameters matched to their analogue III-V semiconductors for use in energy-relevant devices such as LEDs and PV. Disorder-synthesis-property relationships for these materials are not well understood, but new computational techniques can provide information complementary to experimental investigations and reveal the underlying physics of these materials. Using a combination of first principles, cluster expansion, and Monte Carlo methods, we investigated cation disorder in ZnGeN2 and its effect on electronic structure as a function of effective temperature. We identify an order-disorder transition at an effective temperature of 2500K (achievable using nonequilibrium synthesis), where the local environment of nitrogen changes from exclusively 2:2 Zn:Ge coordination to the inclusion of higher energy motifs. Since ordering is a complex effect with implications on multiple length scales, metrics for assessing ordering based on cation site occupancy are compared for disordered structures at effective temperatures above this transition. This study provides insight into the synthesis-property relationship for ZnGeN2 and provides a point of comparison with other ternary semiconductor systems. |
Thursday, March 5, 2020 10:36AM - 10:48AM |
R43.00010: Perfect short-range ordered alloy with line-compound-like properties in the ZnSnN2:ZnO system Stephan Lany, Jie Pan, Jacob Cordell, Garritt Tucker, Andriy Zakutayev, Adele Tamboli Inorganic crystalline materials are either line compounds or solid solutions, and computational materials discovery has so far focused primarily on the former. We here present a new condensed-matter phase which is a disordered solid solution but offers many ordered line-compound features. The emergent physical phenomena are rooted in the perfect short-range order. We model the dual-sublattice mixed semiconductor alloy (ZnSnN2)1-x(ZnO)2x using first-principles calculations, Monte- Carlo simulations with a model Hamiltonian, and an extension of the regular solution model by incorporating short-range order. We demonstrate that this unique solid solution, occurring at a “magic” composition, can provide an electronically pristine character without disorder-induced charge localization and, therefore, a superior carrier transport similar to ordered phases. Interestingly, this phase shows singularities that are absent in the conventional solid-solution models, such as the regular solution and band-gap bowing model. Thermodynamically, this alloy phase has a sharply reduced enthalpy at its composition (like a line compound), but it still requires the entropy from long-range disorder to be stabilized at experimentally accessible temperatures. |
Thursday, March 5, 2020 10:48AM - 11:00AM |
R43.00011: The design of disordered three-dimensional auxetic networks Meng Shen, Marcos Reyes-Martinez, Edwin P Chan, Christopher Soles, Nidhi Pashine, Sidney Robert Nagel, Heinrich M. Jaeger, Juan De Pablo Auxetic materials are characterized by a negative Poisson’s ratio. They have attracted a lot of attention from both the scientific and engineering communities because of a variety of potential applications, such as impact mitigation, indentation resistance and biocompatibility. The design of auxetic materials is usually realized in lattice-based periodic structures in an Edisonian way. Disordered networks have the potential for the design of tunable isotropic auxetic metamaterials. However, the design of disordered three-dimensional auxetic networks has been challenging due to lack of a universal design principle. Here we propose computational strategies for the systematic design of disordered three-dimensional auxetic networks. Our designs are validated by experimental measurement of 3D-printed networks. This work builds a powerful computational framework to manipulate the auxetic properties. |
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