Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E1: Computational Discovery and Design of Novel Materials IVFocus
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Sponsoring Units: DMP DCOMP Room: 260 |
Tuesday, March 14, 2017 8:00AM - 8:36AM |
E1.00001: Soft Functionals for Hard Matter Invited Speaker: Valentino R. Cooper Theory and computation are critical to the materials discovery process. While density functional theory (DFT) has become the standard for predicting materials properties, it is often plagued by inaccuracies in the underlying exchange-correlation functionals. Using high-throughput DFT calculations we explore the accuracy of various exchange-correlation functionals for modeling the structural and thermodynamic properties of a wide range of complex oxides. In particular, we examine the feasibility of using the nonlocal van der Waals density correlation functional with C09 exchange (C09x), which was designed for sparsely packed soft matter, for investigating the properties of hard matter like bulk oxides. Preliminary results show unprecedented performance for some prototypical bulk ferroelectrics, which can be correlated with similarities between C09x and PBEsol. This effort lays the groundwork for understanding how these “soft” functionals can be employed as general purpose functionals for studying a wide range of materials where strong internal bonds and nonlocal interactions coexist. [Preview Abstract] |
Tuesday, March 14, 2017 8:36AM - 8:48AM |
E1.00002: A van der Waals density functional study of 1T’-Td phase transition in semimetallic bulk MoTe2 and WTe2 Hyun-Jung Kim, Ikutaro Hamada, Young-Woo Son Based on the van der Waals density functional (vdW-DF) method, we investigate interlayer interaction and phase stability of orthorhombic (Td ) and monoclinic (1T') form of bulk transition metal dichalcogenides (TMD) MoTe2 and WTe2 . We show that a recently proposed revised version of the vdW-DF2 [I. Hamada, Phys. Rev. B 89, 121103(R) (2014)] functional improves the description of the interlayer interaction, thereby computing their most accurate lattice parameters of T$_d$ and 1T' structure successfully as well as electronic properties while several other methods fail to reproduce them. It is also found that the Td structure is energetically favored over the 1T' structure of both MoTe2 and WTe2 . More interestingly, we found that MoTe2 has a transition energy barrier in T$_d$$\rightarrow$1T' phase transition while WTe2 has no barrier. Such disparate features in transition barrier are consistent with several experimental observations. We will discuss origins of structural phase transition in MoTe2 and its absence in WTe2 [Preview Abstract] |
Tuesday, March 14, 2017 8:48AM - 9:00AM |
E1.00003: Failure of popular density functionals: Torsional potential of conjugated hetero double bonds Diana Tahchieva, Anatole von Lilienfeld Accurate predictions of torsional potential energy profiles are crucial to correctly sample conformational degrees of freedom. Using most of currently popular density functionals we have investigated many small organic closed shell molecules with conjugated hetero double bonds. Typically, density functional theory (DFT) is assumed to provide reasonable energy estimates for such systems and properties. In comparison to CCSD(T), however, all functionals fail to quantitatively reproduce the correct potential, except for M0(5,6)2X and CAM-B3LYP. For molecules containing CO or CS double bonds and heavy halogene atoms even qualitative trends can not be recovered. Analysis of the results reveals that the deviations are due to large errors in the electrostatic potential originating in a failures to generate correct electron densities. Empirical atom centered corrections can rectify some of the short-comings for PBE and BLYP [1].\\ $[1]$ D. Tahchieva, R. Ramakrishnan, O. A. von Lilienfeld, in preparation (2016) [Preview Abstract] |
Tuesday, March 14, 2017 9:00AM - 9:12AM |
E1.00004: Maximum Entropy Method applied to Real-time Time-Dependent Density Functional Theory Yasunari Zempo, Mitsuki Toogoshi, Satoru S. Kano Maximum Entropy Method (MEM) is widely used for the analysis of a time-series data such as an earthquake, which has fairly long-periodicity but short observable data. We have examined MEM to apply to the optical analysis of the time-series data from the real-time TDDFT. In the analysis, usually Fourier Transform (FT) is used, and we have to pay our attention to the lower energy part such as the band gap, which requires the long time evolution. The computational cost naturally becomes quite expensive. Since MEM is based on the autocorrelation of the signal, in which the periodicity can be described as the difference of time-lags, its value in the lower energy naturally gets small compared to that in the higher energy. To improve the difficulty, our MEM has the two features: the raw data is repeated it many times and concatenated, which provides the lower energy resolution in high resolution; together with the repeated data, an appropriate phase for the target frequency is introduced to reduce the side effect of the artificial periodicity. We have compared our improved MEM and FT spectrum using small-to-medium size molecules. We can see the clear spectrum of MEM, compared to that of FT. Our new technique provides higher resolution in fewer steps, compared to that of FT. [Preview Abstract] |
Tuesday, March 14, 2017 9:12AM - 9:24AM |
E1.00005: Exploring the features of $E_n{(\bf k)}$ Andrew Supka, Nicholas Mecholsky, Cormac Toher, Stefano Curtarolo, Marco Buongiorno Nardelli, Marco Fornari The full dispersions, $E_n({\bf k})$, are conventionally represented on specific high-symmetry paths or integrated to determine the density of states. Novel methodologies, developed within the AFLOW consortium, allow analysis of the full energy dispersion efficiently in order to seek for valleys with optimized properties. We discuss results from high-throughput calculations performed with AFLOW$\pi$ to illustrate the importance of the full band structure in the optimization of the electronic transport coefficients. We will focus our discussion on binary chalcogenides. [Preview Abstract] |
Tuesday, March 14, 2017 9:24AM - 9:36AM |
E1.00006: High throughput quantum Monte Carlo calculations of material formation energies Kayahan Saritas, Tim Mueller, Lucas Wagner, Jeffrey C. Grossman High throughput calculations based on approximate density functional theory (DFT) methods have been widely implemented in the scientific community although depending on both the properties of interest as well as particular chemical/structural phase space, accuracy even for correct trends remains a key challenge for DFT. In this work, quantum Monte Carlo calculations are applied using a recipe developed for a high throughput computing environment. We compare our approach to different DFT methods as well as different pseudopotentials, showing that errors in QMC calculations can be progressively improved especially when correct pseudopotentials are used. We show that using this simple automated recipe, QMC calculations can outperform DFT calculations over a wide set of materials. We show that out of 21 compounds tested, chemical accuracy has been obtained in formation energies of 11 structures using our QMC recipe, compared to none using DFT calculations. [Preview Abstract] |
Tuesday, March 14, 2017 9:36AM - 9:48AM |
E1.00007: Band structure diagram paths based on crystallography Yoyo Hinuma, Giovanni Pizzi, Yu Kumagai, Fumiyasu Oba, Isao Tanaka Systematic and automatic calculations of the electronic band structure are a crucial component of computationally-driven high-throughput materials screening. For this purpose, we have derived an algorithm, for any crystal, to derive a unique description of the crystal structure together with a recommended band path [Hinuma \textit{et al}., \underline {http://arxiv.org/abs/1602.06402}, Comp. Mater. Sci., accepted.]. The symmetry of the crystal and restrictions on the electronic band structure at Brillouin zone boundaries, which are independent characteristics, are considered and points in reciprocal space are labeled such that there is no conflict with the crystallographic convention. Most notably, we find that a band path that contains all representatives of special k-vector points must depend on the point group in simple and face-centered cubic as well as hexagonal cells. Furthermore, we provide an open-source implementation of the algorithms within our SeeK-path python code, to allow researchers to obtain k-vector coefficients and recommended band paths in an automated fashion. A free online service to compute and visualize the Brillouin zone, labeled k-points and suggested band paths for any crystal structure is available at \underline {http://www.materialscloud.org/tools/seekpath/}. [Preview Abstract] |
Tuesday, March 14, 2017 9:48AM - 10:00AM |
E1.00008: Organic Materials Database: Electronic Structure Database with Focus on Data Mining Stanislav Borysov, Matthias Geilhufe, Alexander Balatsky We present the Organic Materials Database (OMDB) hosting electronic band structure calculations for thousands of organic and organometallic materials. The electronic band structures are calculated using density functional theory for the crystal structures contained within the Crystallography Open Database. Although these materials were previously synthesized, little attention has been paid to their electronic properties. The OMDB database is freely accessible online at http://omdb.diracmaterials.org. The OMDB web interface allows for identifying materials with certain target band structure and density of states properties specified by the user. We illustrate the use of OMDB and how it can become an organic part of search and prediction of novel functional materials via data mining techniques. [Preview Abstract] |
Tuesday, March 14, 2017 10:00AM - 10:12AM |
E1.00009: AFLOWSYM: A robust procedure to perform the complete symmetry analysis of crystals David Hicks, Corey Oses, Stefano Curtarolo Determination of the symmetry profile of structures is a persistent challenge in materials science as evident from implementation-specific results. Herein, we present a robust procedure for evaluating the complete suite of symmetry operations, including that of the lattice point group, factor group, crystallographic point group, and space group. The protocol resolves a system-specific mapping tolerance, which accounts for variability of error in reported atomic positions. A tolerance is validated through an analysis of the operations it defines, which must all be consistent with fundamental crystallographic principles. The approach has been successfully tested against the Inorganic Crystal Structure Database (ICSD) [1] entries cataloged in the aflow.org [2] online repository. The AFLOWSYM package is implemented within the automatic, high-throughput computational framework AFLOW [3] and is available for public use at aflow.org [3]. [1] FIZ Karlsruhe and NIST, Inorganic Crystal Structure Database, http://icsd.fiz-karlsruhe.de/icsd/ [2] S. Curtarolo et al. Comp. Mater. Sci. 58, 227-235 (2012). [3] S. Curtarolo et al. Comp. Mater. Sci. 58, 218-226 (2012). [Preview Abstract] |
Tuesday, March 14, 2017 10:12AM - 10:24AM |
E1.00010: Universal Fragment Descriptors for Predicting Electronic and Mechanical Properties of Inorganic Crystals Corey Oses, Olexandr Isayev, Cormac Toher, Stefano Curtarolo, Alexander Tropsha Historically, materials discovery is driven by a laborious trial-and-error process. The growth of materials databases and emerging informatics approaches finally offer the opportunity to transform this practice into data- and knowledge-driven rational design---accelerating discovery of novel materials exhibiting desired properties. By using data from the {\small AFLOW} repository for high-throughput, \textit{ab-initio} calculations, we have generated Quantitative Materials Structure-Property Relationship (QMSPR) models to predict critical materials properties, including the metal/insulator classification, band gap energy, and bulk modulus. The prediction accuracy obtained with these QMSPR models approaches training data for virtually any stoichiometric inorganic crystalline material. We attribute the success and universality of these models to the construction of new materials descriptors---referred to as the universal Property-Labeled Material Fragments (PLMF). This representation affords straightforward model interpretation in terms of simple heuristic design rules that could guide rational materials design. This proof-of-concept study demonstrates the power of materials informatics to dramatically accelerate the search for new materials. [Preview Abstract] |
Tuesday, March 14, 2017 10:24AM - 10:36AM |
E1.00011: Finding hot atoms on a cold substrate: a Manganese Oxide Cluster Decorated with Water Jianwei Sun, Mark Pederson Direct conversion of solar energy to fuel is the most beneficial for energy storage and distribution. In naturally occurring photosynthetic systems, it is often the case that an evolutionary designed system has both chromophores, responsible for absorbing light, and a separate reaction center where the absorbed energy is quickly transferred for conversion into chemical energy. It is not immediately clear whether nature has made such choices to avoid radiation damage near the reaction center or due to constraints that biologically assembled energy conversion systems cannot use the Aldrich catalog of chemicals. Thus, a reasonable paradigm is to search over all possible chemical systems and only consider photocatalysts for which the reaction center coincides with the chromophore or is the immediate effective recipient of sunlight through fast first-order stimulated desorptions. Here we propose a general scheme to high-throughput search for stable ``cold'' substrates which have ``hot'' reaction centers that localize the photo-induced electronic state and are in close proximity to a pair of reactants, capable of producing a desired product (possibly H$_{\mathrm{2}}$, O$_{\mathrm{2}}$, NH$_{\mathrm{3}}$, or a hydrocarbon). We use a manganese oxide cluster decorated with water as an example to illustrate the scheme. [Preview Abstract] |
Tuesday, March 14, 2017 10:36AM - 10:48AM |
E1.00012: Formulation of an entropy descriptor for entropy stabilized compounds from high-throughput DFT Pranab Sarker, Cormac Toher, Tyler Harrington, Joshua Gild, Jian Luo, Jon-Paul Maria, Don Brenner, Kenneth Vecchio, Stefano Curtarolo Entropy stabilized compounds such as entropy stabilized borides, carbides, and oxides [C. M. Rost, {\it et al.}, Nat. Commun. \textbf{6}, 8485 (2015)] are an emerging class of materials in the family of chemically disordered high entropy alloys (HEAs), that are highly attractive candidates for ultra-high temperature applications. The prediction of the synthesizability of these materials using {\it ab initio} calculations requires the formulation of a descriptor for the existence of a disordered phase at elevated temperature based only on calculations of ordered phases at $T = 0 K$. Our proposed descriptor is based on the energy distribution of an appropriate ensemble of different ordered configurations, obtained using Density Functional Theory (DFT) and the AFLOW computational materials design framework. This entropy descriptor can predict the propensity of the composition to form an entropy stabilized single-phase material and shows excellent agreement with the experimental results. [Preview Abstract] |
Tuesday, March 14, 2017 10:48AM - 11:00AM |
E1.00013: Conductivity in amorphous chalcogenides. Kiran Prasai, Parthapratim Biswas, David Drabold Metal doped glassy chalcogenides show swift change in conductivity in response to a small external voltage and are being used to make memory elements. We study here the microscopic origin of such conductivity in a canonical material of this category: (GeSe3)xAg100-x. We have used a novel method to electronically design the conducting phase of this material via a biased ab initio MD simulation. We briefly discuss the modeling technique here. We study the models and point out the structural and electronic features of the conducting phase and draw the contrast with their insulating counterparts. We also point out the role of silver clusters/wires in the conductivity by an explicit simulation of such structures with the glassy matrix. [Preview Abstract] |
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