Computational Materials Discovery and Optimization – From Bulk to Materials Interfaces and 2D Materials: Materials Surfaces, Interfaces, and Electrochemistry
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Richard Hennig, University of Florida; Arunima Singh, Lawrence Berkeley National Laboratory; Dallas Trinkle, University of Illinois, Urbana-Champaign; Eric Homer, Brigham Young University

Tuesday 8:30 AM
February 28, 2017
Room: 11A
Location: San Diego Convention Ctr

8:30 AM  Invited
Ab-initio Description of Oxides in an Electrochemical Environment: Mira Todorova1; Anoop Vatti1; Suhyun Yoo1; Joerg Neugebauer1; 1Max-Planck-Institut fuer Eisenforschung GmbH
    Electrochemistry offers a huge amount of possibilities for the design and discovery of new materials, but presents challenges to the quantitative description of materials behaviour because of the involvement of different length scales, time scales and materials classes. Our recently developed unifying approach for semiconductor defect chemistry and electrochemistry [Phys. Rev. Appl. 1, 014001 (2014)] enables us to characterise materials properties in electrochemical environment. Using the example of ZnO we discuss how this method, in conjunction with density functional theory and an implicit solvation model [J. Chem. Phys. 140, 084106 (2014)], can be utilised to study the impact an aqueous electrolyte has on the surface stability of ZnO(0001) surfaces or identify dominant point defects which govern the growth and dissolution of the oxide barrier layer forming when Zn comes into contact with a corrosive environment [Farad. Discussions 180, 97 (2015)].

9:00 AM  
Computational Discovery of Highly Active Catalysts to Enhance Electrochemical Reactions in Li-O2 Batteries: Jianjun Liu1; 1Shanghai Institute of Ceramics, Chinese Academy of Sciences
    Lithium-oxygen batteries are considered as promising energy storage technique because of high specific energy. However, their applications face a large challenge such as high overpotential, poor cycle and rate performance. Developing active catalysts to enhance electrochemical reactions is important to improve their electrochemical performance. Herein, I will focus on unraveling the descriptor of catalytic activity related to physical properties of catalyst. The first-principles calculations based on interfacial model were performed to study the oxygen reduction and evolution reaction mechanisms of Li2O2 supported on active surfaces of transition metal compounds. The O2 evolution and Li+ desorption energies show linear and volcano relationship with surface acidity of catalysts, respectively. Therefore, the charging voltage and desorption energies of Li+ and O2 over TMC could correlate with their corresponding surface acidity. According to this correlation, some highly active catalysts such as Co3O4, Mo2C, TiC, and TiN are predicted by calculations and confirmed by experiments.

9:20 AM  Invited
The Electrostatic Double Layer of Pt/Water Interfaces from First Principles Molecular Dynamics: Clotilde Cucinotta1; 1Trinity College
    The formation of the electrostatic double layer (DL) is the most basic phenomenon taking place at electrified interfaces [1]. However, even in the relatively simple case of a Pt-water interface a realistic description of the equilibrium structure of this DL - accounting for electronic, polarization and solvent reorganization effects – is still missing. In this talk I will discuss strategies and examples on how to address, from a theoretical and computational standpoint, the description of the effect of the application of a potential to an electrochemical cell. I will illustrate a new dynamical model based on first principles, which extends previous schemes to simulate charged electrodes, providing a realistic picture of DL and capacitance of a prototypic Pt-water interface and its response to changes of potential applied to the cell.

9:50 AM  Invited
Metal-Organic Frameworks for Gas Capture and Storage: Computational Discovery and Experimental Validation: Donald Siegel1; 1University of Michigan
    Thanks to their high surface areas, crystallinity, and tunable properties, metal-organic frameworks (MOFs) have attracted intense interest as next-generation materials for gas capture and storage. An often-cited benefit of MOFs is their large number of structures and compositions. However, this design flexibility also has drawbacks, as pinpointing optimal compounds is time consuming and costly using conventional experimental approaches. As a consequence, computational approaches are garnering increasing importance as a means to accelerate the discovery of high-performing MOFs. Here we demonstrate high-throughput techniques for predicting the performance of MOFs for CO2 capture and the storage of gaseous fuels such as methane and hydrogen. Empirical screening strategies are compared with those employing direct atomistic calculations. The performance of the most promising compounds are synthesized and tested experimentally.

10:20 AM Break

10:35 AM  
Machine Learning the Atomistic "Building Blocks" of Grain Boundary Systems: Conrad Rosenbrock1; Gus Hart1; Eric Homer1; Gábor Csányi2; 1Brigham Young University; 2University of Cambridge
    Grain boundary (GB) systems include an uncountably infinite number of possible grain boundaries, with each GB's behavior and properties arising from myriad, atomistic interactions. Is it possible to describe the properties of any GB in the system using knowledge of only a few? If so, which GBs have these essential, atomistic "building blocks" from which all other GB's properties can be predicted? In this talk we present a new, universal similarity metric for grain boundaries based on the Smooth Overlap of Atomic Positions descriptor that provides a rigorous metric of GB similarity with many desirable mathematical properties. We demonstrate its effectiveness by applying the metric to predict grain boundary energy, shear coupling, and mobility using machine learning. We will also show how this new mathematical approach opens the way to decompose GB systems and discover those essential atomistic building blocks that ultimately control these properties.

10:55 AM  
A Theoretical Study of Interfaces between Transition Metals and a-C:H: Matous Mrovec1; Srinivasan Rajagopalan2; Davide Di Stefano1; Christian Elsaesser1; 1Fraunhofer Institute for Mechanics of Materials IWM; 2ExxonMobil Research and Engineering Company
    Solid-solid interfaces can have a decisive impact on mechanical properties in advanced material systems. While interfaces between two crystalline phases have been studied extensively in the past, understanding of interfacial properties for systems composed of crystalline and amorphous phases is still limited. In this work, we have investigated the structure and energetics for a number of interfaces between a transition metal (Ti, Fe) substrate and a thin a-C:H film using atomistic simulations. Both first principles calculations based on density functional theory (DFT) and semi-empirical tight-binding and bond-order approaches have been employed. The former are highly reliable but limited to small systems, the latter enable to sample a broader range of configurations and system sizes while still providing physically correct description of chemical bonding. We analyzed the influence of substrate chemistry and a-C:H film properties (density, sp3/sp2 ratio) on the thermodynamical stability of interfaces and cohesive behavior under external loading.

11:15 AM  Invited
Computational Materials Discovery: From Reduced Pt Catalysts to Lightweight Alloys: Houlong Zhuang1; Alexander Tkalych1; Mohan Chen1; Emily Carter1; 1Princeton University
    Computational tools based on density-functional theory (DFT) play an important role in the design and discovery of novel materials for sustainable energy and environmental applications. We show two examples in this talk. First, we apply Kohn-Sham DFT (KSDFT) to study tungsten carbide covered with monolayer platinum, a promising electrocatalyst with significantly reduced Pt loading. We investigate the dependence of the hydrogen binding energy (HBE) on surface terminations, thickness, and strain. Our calculations reveal the “fingerprint” responsible for the HBE similarity between monolayer Pt/WC and pure Pt. Second, we study the elastic and thermodynamic properties of four stoichiometric magnesium-aluminum compounds with orbital-free density functional theory (OFDFT). We compute the phonon spectra using the force constants extracted from the OFDFT calculations. Our work demonstrates that OFDFT is an efficient and accurate quantum-mechanical tool for predicting elastic and thermodynamic properties of complicated Mg-Al alloys and should also be applicable to many other alloys.

11:45 AM  
High-throughput Screening on Relationship between Selectivity and Working Capacity of Porous Materials for Propylene/Propane Adsorptive Separation: Byung Chul Yeo1; Sang Soo Han1; 1Korea Institute of Science and Technology
    Gas separation technology between propane/propylene is very important in the petrochemical industry. Here, several intriguing questions arise in the practice of the gas separation: 1) what is the best porous material for propane/propylene separation? and 2) what's the most significant property for improving the gas separation? To answer these questions, we perform high-throughput screening (HTS) approach from the Cambridge Structural Database (CSD) and Inorganic Crystal Structural Database (ICSD) along with a grand canonical Monte-Carlo simulation, and the total number of all crystal structures is approximately 1,000,000. As indicators of gas separation performance, selectivity and working capacity can be considered. In this work, we clarify correlations between physical properties of porous materials (e.g. heat of adsorption, surface area, and pore volume) and selectivity/working capacity from the HTS approach. To our best knowledge, this work is the first study to apply to the HTS approach in a field of gas separation.

12:05 PM  
A Study on the Effects of Temperature and Composition on the Templated Two-Phase Growth of a Thin Film by the Means of Computer Simulation: Xiao Lu1; Jian-Gang Zhu2; David Laughlin2; Jingxi Zhu1; 1Sun Yat-sen University-Carnegie Mellon University Joint Institute of Engineering,; 2Carnegie Mellon University
    In the process of template growth of two phase film, the pre-fabricated template, with optimized geometric features, can guide the simultaneous growth of the two immiscible phases during deposition to obtain the most desirable microstructure. A hybrid simulation model that incorporates Potts Model Monte Carlo and Level Set Method was developed previously to study the physical mechanism behind this process. In this study, this model was used to study the effects from the parameters used in template two-phase growth. One attempt was made to study the effect of deposition temperature on microstructure by establishing the relation between the lattice temperature used in simulation to the thermal fluctuation during experimental deposition. The selection of materials and the composition of the film were also investigated. A comparison was made between CoPt-SiO2 film deposited at room temperature and FePt-X (X stands for a non-metallic material) films deposited at elevated temperature up to 700şC.