Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P26: Computational Discovery and Design of Novel Materials VIIFocus
|
Hide Abstracts |
Sponsoring Units: DCMP DCOMP Chair: Chris van de Walle, UCSB Room: 289 |
Wednesday, March 15, 2017 2:30PM - 3:06PM |
P26.00001: Identification of nonradiative recombination centers in GaN Invited Speaker: Darshana Wickramaratne Defect-assisted recombination limits the efficiency of solid-state devices. Since nonradiative capture rates decrease exponentially with the energy of the transition, the mechanisms by which recombination take place in wide-band-gap materials are unclear. We will discuss the methodology we have developed to address nonradiative recombination rates from first principles [1], and illustrate its application with the important case of Fe in GaN [2]. Research on Fe has been motivated by the use of Fe to achieve semi-insulating GaN substrates and room-temperature ferromagnetism in GaN. Iron can also be introduced unintentionally into GaN during growth. In traditional semiconductors such as silicon, transition metal impurities are known to act as efficient Shockley-Read-Hall centers by introducing midgap defect levels. Iron impurities in GaN do not follow this pattern: their defect level is close to the conduction band, and hence iron is not expected to act as a strong nonradiative recombination center. We use first-principles calculations based on density functional theory with a hybrid functional to uncover the electronic properties of Fe in GaN. We demonstrate that its high efficiency as a nonradiative center is due to a recombination cycle involving excited states. Unintentional incorporation of iron impurities at modest concentrations leads to nanosecond nonradiative recombination lifetimes. These calculations provide insight into the mechanisms that govern efficient nonradiative recombination in wide-band-gap semiconductors, which is essential for engineering improved materials to be adopted in efficient devices. This work was performed in collaboration with J.-X. Shen, C. E. Dreyer, G. Kresse, S. Marcinkevicius, A. Alkauskas, and C. G. Van de Walle. [1] C. E. Dreyer et al., Appl. Phys. Lett. 108, 141101 (2016). [2] D. Wickramaratne et al., Appl. Phys. Lett. 109, 162107 (2016). [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P26.00002: Electronic properties of ultra-wide-band-gap nitride alloys from first principles Jimmy-Xuan Shen, Darshana Wickramaratne, Chris Van de Walle Boron-containing nitride alloys such as BAlN and BGaN are being explored as novel members of the nitride family for electronic and optoelectronic applications. The design of materials and devices for such applications requires a fundamental understanding of the composition-dependent electronic structure. At low B content, the materials stabilize in the wurtzite structure; BN itself is not stable in the wurtzite structure, and therefore no experimental information is available to allow predictions for the B-containing alloys. In this work, we employ density functional theory with a hybrid functional to investigate the electronic structure of B-containing alloys as a function of boron content. Wurtzite BN is an indirect band-gap semiconductor, while AlN and GaN have a direct band gap; we therefore expect a crossover from direct to indirect band gap as a function of increasing B content. We also expect large band-gap bowing due to the large lattice mismatch between the parent compounds. We are able to accurately identify the direct-to-indirect crossover by using a projection scheme. We find that the bowing parameter for the direct band gap is much larger than for the indirect gap. We also investigate the sensitivity of these properties to the B distribution. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P26.00003: Acoustic-optical phonon branch crossings and lattice thermal transport in La$_3$Cu$_3$X$_4$ (X = P, As, Sb, and Bi) systems Tribhuwan Pandey, Carlos A. Polanco, Lucas Lindsay, David S. Parker Thermoelectric properties of La$_3$Cu$_3$X$_4$ (X = P, As, Sb, and Bi) compounds are examined using first-principles density functional theory and Boltzmann transport calculations. It is well known that the lattice thermal conductivity ($\kappa_{l}$) of bulk materials typically decreases with increasing atomic masses of the constituent elements. In this study, however, we observe contrary behavior: lighter mass, larger sound velocity La$_3$Cu$_3$P$_4$ and La$_3$Cu$_3$As$_4$ systems have lower $\kappa_{l}$ than heavier mass, smaller sound velocity La$_3$Cu$_3$Sb$_4$ and La$_3$Cu$_3$Bi$_4$ systems. Analysis of three phonon scattering rates and other phonon properties demonstrate that the trend in $\kappa_{l}$ behavior is governed by Gr\"{u}neisen parameters, a measure of phonon anharmonicity. The Gr\"{u}neisen parameters and lower $\kappa_{l}$ of the P and As compounds are closely related to an avoided crossing between the lowest optical branches and the longitudinal acoustic branch, which results in abrupt changes in Gr\"{u}neisen parameters. Additionally, electronic structure calculations show heavy and light bands near the band edges, which lead to large power factors important for good thermoelectric performance. [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P26.00004: Polymorphism in transition metal compounds: An LDA+Rotationally-invariant slave-boson study Tsung-Han Lee, Nicola Lanata, Yongxin Yao, Vladan Stevanovic, Vladimir Dobrosavljevic Treating the strong correlation effect in transition metal compounds is a challenging task in first principle simulation, where standard approximations to density functional theory (DFT) usually fail to predict correct ground-state structure and energy ordering among different polymorphs due to the lack of appropriate electron correlation description. In this talk, we show that, within the framework of local density approximation(LDA) plus rotationally-invariant slave-boson(RISB) approach, we are able to recover the correct ground state structure, electronic phases and reasonable equilibrium volumes for 6 transition metal compounds; CrO, MnO, FeO, CoO, CoS, and CoSe, among the rocksalt, zincblende, NiAs, and wurtzite structures. This result demonstrates the potential of LDA+RISB as an accurate and efficient tool for investigating strongly correlated materials and predicting their structures. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P26.00005: Band unfolding scheme for one-dimensional semiconductor nanowires Sunghyun Kim, Kee Joo Chang First-principles density functional calculations have been widely used to investigate the electronic structure of a variety of materials. Recently, one-dimensional nanostructures such as nanowires have received much attention because of their unique electronic properties and their building blocks of nanoscale devices. Due to quantum confinement and zone folding effects, semiconductor nanowires exhibit a complex subband structure different from those of their bulk counterparts. Using a band unfolding method, one can extract the hidden translational symmetry and compare directly the unfolded band structure with experiments such as angle resolved photoemission spectroscopy measurements. In one-dimensional systems embedded in vacuum, since confined modes exist, correspondence between the supercell and primitive reciprocal spaces is not well defined compared with perfect bulk systems. In this work, we propose a scheme for unfolding the band structure of semiconductor nanowires, in which a localized basis set is used for the band unfolding. The nanowire wave functions are described in terms of Bloch waves along the periodic wire axis and confined standing waves across the wire. For Si nanowires, we find that the unfolded band structure well recovers the hidden dispersion of bulk Si, verifying our scheme, and discuss the usefulness. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P26.00006: From tetrahedral networks to (meta-) stable ice structures: a theoretical study Edgar Engel, Chris Pickard, Richard Needs, Michele Ceriotti, Andrea Anelli We present a comprehensive computational study of the crystalline phases of water ice employing force field and dispersion corrected density functional theory calculations. We construct ice structures on the basis of more than five million tetrahedral networks listed in the Treacy, Deem, and IZA databases and employ the ``Sketchmap'' dimensionality reduction algorithm of Ceriotti et al. to examine the thus explored configuration space. Assuming no prior knowledge of the known stable phases of water ice, we classify the structures and recover all but two of ices I to XVI and ices i, 0 and the quartz phase of ice. More importantly, we identify them as the most stable representatives of their respective clusters of alike structures. We further identify 10 new dynamically stable structures with competitive enthalpies compared to the know phases of ice. For these we perform anharmonic quantum nuclear vibrational calculations using the VSCF methods of Monserrat et al. We find that two of these structures compare favourably to the theoretical i and 0 phases at similar densities, with one matching the structure recently proposed for ice XVII on the basis of neutron diffraction data. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P26.00007: Crystal structure prediction supported with diffraction data Naoto Tsujimoto, Daiki Adachi, Synge Todo, Ryosuke Akashi, Shinji Tsuneyuki Atomistic computer simulation is of growing importance in the study of unidentified crystals, although prediction or determination of complicated structure is still a challenging problem due to its many degrees of freedom. Here we propose to utilize experimentally available data of powder diffraction to support and accelerate the structure simulation. In so-called direct-space methods for structure determination from powder diffraction, simplified interatomic potential energy or some other physical constraints are often used in combination with the cost function defined by diffraction data (R.\v{C}ern\'{y} and V. F. Nicolin, Z. Kristallogr. ${\bf222}$, 105 (2007)). On the other hand, we formulate a cost function called ``crystallinity" to support simulation with accurate interatomic potential energy. Since the crystallinity here is defined as the sum of the diffraction intensities only at the peak positions detected in experiments, this method is applicable to low-quality diffraction data such as those obtained at high pressures. We apply this method to well-known polymorphs of $\rm{SiO_2}$ with up to 96 atoms in the simulation cell to find that it reproduces the correct structures efficiently with information of a very limited number of diffraction peaks. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P26.00008: The Thermodynamic Scale of Inorganic Crystalline Metastability Wenhao Sun, Stephen Dacek, Shyue Ping Ong, Geoffroy Hautier, Anubhav Jain, William Richards, Anthony Gamst, Kristin Persson, Gerbrand Ceder The space of metastable materials offers promising new design opportunities for next-generation technological materials such as complex oxides, semiconductors, pharmaceuticals, steels and beyond. Although metastable phases are ubiquitous in both nature and technology, only a heuristic understanding of their underlying thermodynamics exists. Here we report a large-scale data-mining study of the Materials Project, a high-throughput database of DFT-calculated energetics of ICSD structures, to explicitly quantify the thermodynamic scale of metastability for 29,902 observed inorganic crystalline phases. We reveal the influence of chemistry and composition on the accessible thermodynamic range of crystalline metastability for polymorphic and phase-separating compounds, yielding new physical insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compounds can necessarily be synthesized, and propose a principle of ``remnant metastability'' -- that observable metastable crystalline phases are generally remnants of thermodynamic conditions where they were once the lowest free-energy phase. [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P26.00009: Role of Features in the Adaptive Design of Materials Prasanna V. Balachandran, Turab Lookman In materials informatics, features or descriptors that capture trends in the structure, chemistry and/or bonding are crucial. Here, we explore their role in the accelerated search for new materials with a targeted response. To accomplish the objective, we construct two datasets that uses two sets of features (ionic radii and electronegativity) and independently track their progress to determine which of the two would rapidly find the optimal composition with the largest band gap (E$_\textrm{g}$). We model the feature--E$_\textrm{g}$ relationship using support vector regression (SVR), which we subsequently utilize for predicting the E$_\textrm{g}$ for the unexplored compositions with uncertainties. Our results show that the ionic radii feature set, despite its relatively poor model fit and large uncertainties, performed better and found the optimal material in fewer iterations compared to the electronegativity feature set, which intriguingly had superior model fit. Visualization of the SVR response surface showed that the the ionic radii feature set led to a far greater exploration of the chemical space, which we attribute as an important diagnostic for accelerated search. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P26.00010: Thermomechanical properties in the AFLOW distributed database Cormac Toher, Corey Oses, Jose J. Plata, David Hicks, Frisco Rose, Ohad Levy, Maarten de Jong, Mark Asta, Olexandr Isayev, Alexander Tropsha, Marco Fornari, Marco Buongiorno Nardelli, Stefano Curtarolo The integrated AEL-AGL workflow [1] has been used to automatically calculate the thermal and elastic properties for over 3000 materials in the AFLOW computational materials data repository [2, 3, 4]. This data set can be used in combination with the AFLOW Search API to screen for candidate materials for applications such as thermoelectrics, heat sinks and thermal barrier coatings. The data set has also been used to train machine learning models for thermomechanical properties, which has been successfully used to predict properties including the bulk modulus and the Debye temperature for tens of thousands of materials. [1] C. Toher et al., Phys. Rev. B 90, 174107 (2014). [2] S. Curtarolo et al., Comp. Mat. Sci. 58, 218 (2012). [3] S. Curtarolo et al., Comp. Mat. Sci, 58, 227 (2012). [4] http://aflow.org/ [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P26.00011: Ab initio structure prediction of silicon and germanium sulfides for lithium-ion battery materials Connie Hsueh, Martin Mayo, Andrew J. Morris Conventional experimental-based approaches to materials discovery, which can rely heavily on trial and error, are time-intensive and costly. We discuss approaches to coupling experimental and computational techniques in order to systematize, automate, and accelerate the process of materials discovery, which is of particular relevance to developing new battery materials. We use the \textit{ab initio} random structure searching (AIRSS) method to conduct a systematic investigation of Si--S and Ge--S binary compounds in order to search for novel materials for lithium-ion battery (LIB) anodes. AIRSS is a high-throughput, density functional theory-based approach to structure prediction which has been successful at predicting the structures of LIBs containing sulfur [1] and silicon and germanium [2]. We propose a lithiation mechanism for Li-GeS$_2$ anodes as well as report new, theoretically stable, layered and porous structures in the Si--S and Ge--S systems that pique experimental interest.\\ [1] C. George, A. J. Morris, M. H. Modarres, and M. De Volder, Chem. Mater. 28, 7304 (2016). [2] A. J. Morris, C. P. Grey, and C. J. Pickard, Phys. Rev. B 90, 54111 (2014). [Preview Abstract] |
Wednesday, March 15, 2017 5:06PM - 5:18PM |
P26.00012: Electrostatic screening in supercell calculations of formation energies of charged-defects Yuning Wu, Sokrates Pantelides, Xiaoguang Zhang Density functional theory calculations of the formation energies of charged defects use a uniform compensating (jellium) background to screen the electrostatic interactions between the supercells. This approximation may cause large errors in complex materials where the screening charge may be different on different sublattices. Here we recognize that charged defects exist in overall neutral systems and develop a more realistic approach to calculate formation energies of charged defects. We use density functional theory and calculate formation energies for vacancies in Si, GaN, and ZnO. We find significant differences from the usual calculations in both the neighboring atom displacements and the formation energies. The common unphysical result that vacancy formation energies become negative when the Fermi energy approaches the conduction-band edge is greatly improved. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700