Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session P56: Computational Design and Discovery of Novel Materials: New Structures, Alloys and Synthesis RoutesFocus Live
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Sponsoring Units: DMP DCOMP Chair: Ruoxi Yang, Lawrence Berkeley National Laboratory |
Wednesday, March 17, 2021 3:00PM - 3:36PM Live |
P56.00001: Toward Rational Discovery and Design of Metastable Materials Invited Speaker: Vladan Stevanovic Metastable materials, both crystalline and amorphous, are invaluable in our daily lives. Classic examples include diamond, glass, or solid chocolate. However, despite the relevance of metastable materials and despite a rather extensive knowledge of the phenomenology of metastability, our ability to rationally discover and design metastable forms of matter is rather limited. In this talk I will present our recent attempts to resolving some of the issues hindering rational discovery and design of functional metastable phases. More specifically, I will discuss the experimental realizability of metastable polymorphs in connection to various features of the potential energy surface1 that can be assessed using modern first-principles calculations leading to a robust methodology to identifying realizable metastable states. Next, I will talk about our efforts in developing computational methods to enable large-scale assessment of the kinetics of polymorphic transformations2,3 predicated on the novel solution to the problem of finding an optimal atom-to-atom mapping between infinitely periodic systems. Lastly, I will present an alternative description of covalent and ionic glassy solids as statistical ensembles of crystalline local minima on the potential energy surface,4 which opens the door to fully predictive approaches without the need for experimental inputs. |
Wednesday, March 17, 2021 3:36PM - 3:48PM Live |
P56.00002: Predicting the phase stability of high entropy oxides Krishna Pitike, Markus Eisenbach, Craig A. Bridges, Valentino Cooper High entropy, multicomponent systems are interesting due to the role that cation disorder may play in defining their mechanical, magnetic, reversible energy storage, thermal insulation, catalytic properties etc. Within the class of high entropy oxides; rock salt, fluorite, spinel and perovskite phases have been recently synthesized. Complementing these endeavors, the current work explores a method for calculating the stability of high entropy oxides through a collaborative computational and experimental efforts. We construct a nearest neighbor model (NNM) from enthalpies of end member and binary oxides – estimated through DFT calculations. The candidates for the high entropy oxides are predicted from the configurational landscapes of the five component oxides, estimated through Monte Carlo simulations using the NNM. Our approach allows us to evaluate potential impurity phases and oxygen vacancy concentration as a function of temperature and oxygen partial pressure, thereby making realistic predictions that can direct and accelerate synthesis of novel multicomponent oxides. |
Wednesday, March 17, 2021 3:48PM - 4:00PM Live |
P56.00003: Novel high-pressure phases in the Nb-S system Roman Lucrezi, Christoph Heil We explore the phase diagram of the binary Nb-S system from ambient pressures up to 250 GPa using ab initio evolutionary crystal structure prediction. We find several new stable compositions and phases, especially in the high-pressure regime, and investigate their electronic, vibrational, and superconducting properties. Our calculations reveal an intricate phase diagram with distinct building blocks in materials with 2D and 3D character, where all binary phases are superconducting metals. |
Wednesday, March 17, 2021 4:00PM - 4:12PM Live |
P56.00004: Effect of alloying and pressure in the structural transition of AsxP1-x system: A first principle study Md Rajib khan Musa, Kazi Jannatul Tasnim, Manthila C Rajapakse, Jacek Bogdan Jasinski, Gamini Udaya Sumanasekera, Ming Yu Layered black arsenic-phosphorus alloy (b-AsxP1-x) is an emerging material in optoelectronics and electronics applications. In addition to its anisotropic behavior, like black phosphorus (b-P), b-AsxP1-x exhibits a narrow bandgap and improves environmental stability. Pure Phosphorus in ambient pressure prefers A17 phase where pure Arsenic prefers A7 phase. Alloying As into b-P could induce a phase transition. A previous theoretical study on AsxP1-x monolayer found the coexistence of A17 and A7 phases at x=0.07 [1]. Based on the finding, we proposed a hypothesis that there may also exist a transformation from the pure Arsenic with A7 structure to layered b-AsxP1-x with A17 structure. In this study, we concentrated on alloying as a means of structural transition and then studied the effect of pressure on this structural phase transition. To accomplish our goal, we thoroughly searched the large compositional space of AsxP1-x alloy to find the critical composition for such phase transition. Afterward, the resulting system is subjected to isotropic hydrostatic pressure to study structural and electronic changes. |
Wednesday, March 17, 2021 4:12PM - 4:24PM Live |
P56.00005: High Throughput Discovery of Inorganic Compounds Sean Griesemer, Cheol Park, Christopher Wolverton With the development of machine learning (ML) tools, we can now automate the prediction of new inorganic compounds. Promising examples of ML tools include the Data Mining Structure Predictor (DMSP), [1] ionic substitution predictor, [2] and improved crystal graph convolutional neural network (iCGCNN). [3] Furthermore, we can now confirm the stability of these compounds using density functional theory (DFT) databases, such as the Open Quantum Materials Database (OQMD). [4] Leveraging these tools, we performed high throughput predictions of thousands of new inorganic compounds. We discuss each ML model and describe the new compounds. For example, we found that the DMSP and iCGCNN were well suited to discover metallic compounds, while the ion substitution successfully predicted ionic compounds. We also discuss specific areas of interest such as mixed anion compounds and double perovskites. |
Wednesday, March 17, 2021 4:24PM - 5:00PM Live |
P56.00006: Predicting the Synthesis and Synthesizability of Novel Computationally-Designed Materials Invited Speaker: Wenhao Sun Despite rapid progress in the computational design of novel functional materials, the materials |
Wednesday, March 17, 2021 5:00PM - 5:12PM Live |
P56.00007: Modeling Atomic Layer Deposition of Alumina as an Ultra-thin Tunnel Barrier using Reactive Molecular Dynamics Devon Romine, Ridwan Sakidja, Judy Zhihong Wu, Yuxuan Lu In this study, we utilized the reactive molecular dynamics (MD) to simulate the Atomic Layer Deposition (ALD) process to form an ultra-thin tunnel barrier made of alumina. We chose reactive MD over the ab-initio molecular dynamics simulation for to its lower computational cost, its ability to model over a relatively longer period and its capability to assess atomistic-based dynamics for a larger substrate. We systematically evaluated the role of the various ALD precursors including the thrimethylaluminum (TMA) and Bis(2-ethyl-1,3-cyclopentadien-1-yl)magnesium (C14H18Mg) and the water pulse toward the chemical reactions that take place on the surface during ALD. We additionally evaluated the role of experimentally- observable parameters including the operating temperature and precursor concentrations for the internal structure of the amorphous alumina/magnesium as the final deposition products. Lastly, we assessed the role of wetting layers as the means to improve the quality and performance of the tunnel barrier. |
Wednesday, March 17, 2021 5:12PM - 5:24PM Live |
P56.00008: Stability of atomic structures in the Al-Co-Cu quasicrystal phase Yang Huang, Michael Widom, Marek Mihalkovic We perform replica-exchange Monte Carlo/molecular dynamics simulations that allow swapping between different chemical species in large crystalline approximants in order to discover optimal atomic configurations. We fit density functional theory energies and forces to empirical oscillating pair potentials (EOPP) which are characterized by short-range repulsion and long-range Friedel oscillations. We perform a series of simulations for the AlCoCu quasicrystal at various compositions and densities with temperatures ranging from room temperature to beyond the melt point. Among these resulting low energy structures, we observe ten-fold symmetry and we are able to distinguish particular tiling patterns when connecting transition metal bonds. We further carry out density functional energy calculation and confirm our best structure to be only 9meV/atom above the convex hull, suggesting the AlCoCu quasicrystal phase may be entropically stabilized at elevated temperatures. |
Wednesday, March 17, 2021 5:24PM - 5:36PM Live |
P56.00009: Natural harmony by an irrational metric in hierarchic icosahedra Antony Bourdillon How does diffraction occur in quasicrystals where the order is irrational and in geometric series? The structure is known to be aperiodic with multiple interplanar spacings. These features, individually and collectively, falsify Bragg diffraction in these solids. An extra variable is needed to account for the irrational and geometric diffraction. This is examined numerically by a modified structure factor method, and analyzed with Fibonacci series in threefold dimensionality. The natural, semi-integral part of any irrational index is separated from its irrational residue which, in turn, forms a special metric function that is universal in the diffraction. The metric harmonizes the irrational index in coherent diffraction from the hierarchic icosahedra. It does this by scaling the harmonic and digital diffraction to the irrational and geometric indexation. [Journal of Modern Physics, (2020) 11, 581-592. doi: 10.4236/jmp.2020.114038 ] |
Wednesday, March 17, 2021 5:36PM - 5:48PM On Demand |
P56.00010: Anisotropic dielectric function response of Ag-Au alloys evaluated via DFT Hiago Maurilio Lopes Carvalho, Mariama Rebello, Anibal Thiago Bezerra The accurate analysis of the optical and electronic properties of noble metals alloys is crucial to develop more efficient devices applied to optoelectronics and medical fields. Particularly, the use of first-principle calculations of silver (Ag) and gold (Au) nanoparticles (NPs) showed that they are promising candidates for the treatment of COVID-19. In this work, we calculate the band structure, the density of states, and the dielectric function (DF) of three Ag-Au alloys and their pure counterparts through the Density Functional Theory (DFT). We show that isotropic responses of the dielectric function is obtained for all systems except for a Ag0.5Au0.5. To validate our results, we compare them with several ones obtained experimentally from the literature. For the Ag0.5Au0.5 system, we see an inconsistency in the dielectric function's reported values in terms of the intra- and interband transition. Those values fall into two categories, matching the ones found in the anisotropic results. The method developed here can be extended to other metallic systems providing an accurate description of their optical response. |
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