Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S43: Computational Design and Discovery of Novel Materials IV: 2D and Layered MaterialsFocus
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Sponsoring Units: DCOMP DMP Chair: Kai-Ming Ho, Iowa State University Room: 702 |
Thursday, March 5, 2020 11:15AM - 11:51AM |
S43.00001: Computational Discovery at the Interface of Chemistry and Materials: 1D Carbon Nanothreads and 2D Polar Metals Invited Speaker: Vincent Crespi The total number of equilibrium crystal structures composed from subsets of the periodic table is likely bounded fairly strictly by phase separation of multi-component mixtures. In contrast, the design space afforded by metastable structures is essentially unbounded: the key challenge here is to craft kinetic constraints that access structures with compelling properties. One strategy to this end deploys the immense design power of synthetic organic chemistry within a solid-state context to produce carbon nanothreads of diverse compositions and properties as ordered lattices comprising uniquely one-dimensional sp3 or mixed sp2/sp3 macromolecules at the ultimate juncture between crystalline rigidity and molecular control. These systems exhibit unique behaviors as the thinnest possible objects whose rigidity is maintained by covalent bonds. In two dimensions, kinetic control in service of unique structure can also be obtained by crafting similarly unique synthesis "containers", for example the gallery between silicon carbide and epitaxial graphene, which can host a broad family of epitaxial, air-stable, crystalline two-dimensional polar metals with record-breaking optical nonlinearities, excellent surface-enhanced Raman performance, and intriguing prospects for the integration of metals into quantum heterostructures. In both cases, predictive computational theory can provide strong guiding principles. |
Thursday, March 5, 2020 11:51AM - 12:03PM |
S43.00002: Robust Half-Metallicity and Perfect Spin Filtering in 2D oxide layer Arqum Hashmi, Kenta Nakanishi, Muhammad Umar Farooq, Tomoya Ono We use first-principles calculations to demonstrate the transition metal oxide monolayer (ML) of Cr2O3 as an ideal candidate for next-generation spintronics applications. Cr2O3 ML has a honeycomb-kagome lattice that possesses the kagome band characteristics, where the Dirac and strongly correlated fermions coexist around the Fermi level. Furthermore, the classical Heisenberg Hamiltonian shows strong FM interactions between Cr spins, and the Cr3+ ions are in a low-spin state leading to a spin S = 3/2. Cr2O3 ML possesses a robust half-metallic behavior with a large spin gap of ~ 3.9 eV and a high TC = 190 K. We also find that Cr2O3 ML displays an intrinsic Ising ferromagnetism with a giant PMAE of ~ 0.9 meV. More importantly, NEGF calculations reveal that the Cr2O3 ML exhibits an excellent spin filtering effect. |
Thursday, March 5, 2020 12:03PM - 12:15PM |
S43.00003: Giant polarization charge density at ScN/GaN interfaces Nicholas Adamski, Cyrus Dreyer, Chris Van de Walle
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Thursday, March 5, 2020 12:15PM - 12:27PM |
S43.00004: Quasi-Binary Transition Metal Dichalcogenide Alloys: Thermodynamic Stability Prediction, Scalable Synthesis and Application Zahra Hemmat, John Cavin, Alireza Ahmadiparidari, Alexander Ruckel, Sung Beom Cho, Robert Klie, Rohan Mishra, Amin Salehi-Khojin Quasibinary alloying in transition metal dichalcogenides (TMDCs) has been successfully used to improve applications including optoelectronics and catalysis. However, the vast compositional space of possible TMDC alloys remains largely unexplored. To guide the synthesis of such alloys, we present ab-initio calculations of equilibrium phase diagrams for 25 TMDC alloys: M1-x M'xX2 and MX2(1-x) X'2x (M,M'= V, Nb, Ta, Mo, W; X,X'= S, Se). We verify the predictions made by these phase diagrams by synthesizing a subset of 12 alloys using scalable chemical vapor transport. We demonstrate the ability to exfoliate these alloys into few-layers. One of these alloys, Nb1-xTaxS2, is shown to have outstanding thermal stability, exceptional CO2 reduction activity with near zero overpotential, and excellent energy efficiency in a Li-air battery. Our work highlights the large number of TMDC alloys accessible to a scalable synthesis-process. By expanding beyond group VI TMDC alloys, this study lays the groundwork for studying how alloying in group V TMDCs affects novel properties such as superconductivity, magnetism, and topological properties. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S43.00005: First-principles prediction of optomechanically controlling phase transition of IV-VI semiconductors Jian Zhou Diffusional phase-change materials, such as Ge-Sb-Te alloys, are used in rewritable nonvolatile memory devices (PC-RAM). This order-disorder transition contains a large latent heat and requires breaking of chemical bonds. It is thus highly desired to develop new phase change materials with diffusionless and order-to-order transitions to accelerate the read/write kinetics, reduce energy dissipation, and eliminate fatigue. Two-dimensional materials are considered as potential phase change materials. For example, one famous 2D material example is transition metal dichalcogenide monolayer which exists in 2H and 1T′ structures. However, it always requires mechanical, electrical, or electrochemical contacts and patterning to trigger phase transition. Non-contacting optical readout/write with focused laser would be preferable in many circumstances, especially for low-dimensional materials which are easily optically accessible. Here, we computationally illustrate an optomechanical strategy, which uses a linearly polarized laser pulse with selected frequency. We will give a few examples of such ultrafast diffusionless martensitic phase transition in various materials. With no or only a few chemical bonds breaking, the phase transition would occur very fast and requires low energy input. |
Thursday, March 5, 2020 12:39PM - 12:51PM |
S43.00006: Predicting synthesizable multi-functional edge reconstructions in two-dimensional transition metal dichalcogenides Guoxiang Hu, Anh Pham, Victor Fung, Xiahan Sang, Raymond Unocic, Panchapakesan Ganesh Two dimentional transition metal dichalcogenides have attracted great interest due to their exceptional properties, especially at the edges. Recently, more complex edge reconstructions were discovered experimentally. This poses intriguing questions: what is the whole family of synthesizable reconstructed edges and what are they good for? Here, we develop a high-throughput ab initio based computational approach to shed light on this. Using MoS2 as a model, we screened hundreds of edge configurations, leading to predictions of new reconstructions with record thermodynamic stability in addition to the discovered ones. We find that the reconstructed edges can be optimized as catalysts for a wide range of reactions and suited for applications in information storage, spintronics, and topologically protected dissipationless transport from their exhibited wide distribution of work function, half-metallicity, magnetic variations, and intriguing topologically protected edge-states.1,2 Our work reveals the existence of a wide family of synthesizable, reconstructed edges, thereby opening a new field of intrinsic edge engineering of 2D materials as multifunctional materials. |
Thursday, March 5, 2020 12:51PM - 1:03PM |
S43.00007: Hybrid assemblies of two-dimensional octagonal monolayers of C and BN Prashant Vijay Gaikwad, Anjali Kshirsagar In the dominating regime of hexagonal family, 2D octagonal monolayers (o-MLs) have emerged recently. High coordination cluster assembly route [J. Phys.: Condens. Matter 29, 335501 (2017)] is employed to form o-MLs of C and BN and their hybrid assemblies. The o-MLs are dynamically and thermally stable. Most of the MLs reveal charge transfer among atoms and asymmetric sp2 hybridization. Hybrid assemblies can be tuned from metallic to insulating (4.13 eV). Stacking of zigzag buckled o-MLs forms stable body centered tetragonal bulk phase of C and BN. Dynamically stable nanotubes (NT), obtained by cutting chunk, with diameter 3.6 Å and 3.57 Å for o-C and o-BN respectively, can also be realized as vertically stacked o-rings and can be contrasted with the rolling of hexagonal ML. We thus report a CNT with a size smaller than the reported theoretical limit and synthesized experimentally till now. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S43.00008: Theoretical studies on excitonic and half-metallic properties in 2D chalcogenides Xiaolong Zou, NanNan Luo, Shuqing Zhang In this talk, I will present theoretical investigation on two classes of chalcogenides with interesting properties, i.e., the saddle-point excitons and half-metallicity. First, monolayer b- and γ-phase group-IV monochalcogenides (MX, M = Ge or Sn; X = S or Se) are shown to possess saddle-point and camel’s back like band structure, respectively. While saddle-point exciton in b-MX leads to its strong adsorption, render them promising for solar cell applications with power conversion efficiencies as large as 1.11%,[1] a high-temperature exciton gas to electron-hole liquid transition can be achieved in γ-MX. Second, a class of CoGa2X4 (X= S, Se or Te) monolayer with triangular lattice exhibits intrinsic in-plane half-metallic ferromagnetism. The half-metal gaps are large enough (about 0.5 eV) to make them stable against the spin flip under weak external disturbances. We have systematically investigated the underlying origin of the ferromagnetism and predicted their high transition temperature TC.[2] |
Thursday, March 5, 2020 1:15PM - 1:27PM |
S43.00009: New 2D massless Dirac fermion systems and quantum spin Hall insulators based on sp–sp2 carbon sheets Minwoo Park, Youngkuk Kim, Hoonkyung Lee Graphene was identified as a quantum spin Hall (QSH) insulator when considering spin-orbit coupling (SOC), which opens a band gap at the Dirac points. This discovery has initiated new research efforts to study the QSH effect on its application for quantum computing and spintronics. Nevertheless, the SOC strength of graphene is too small (~40 µeV) to induce the topological insulator phase in an experimentally achievable temperature regime. Here, we design two-dimensional sp–sp2 hybrid carbon sheets to discover new Dirac systems, hosting the QSH phase. We find that 21 out of 31 new carbon sheets are identified as Dirac fermion systems without SOC, distinct from graphene in the number, shape, occurring Dirac cones. Furthermore, we find 19 out of the 21 new Dirac fermion systems become QSH insulators with a sizable SOC gap. It is enhanced up to an order of meV, allowing for the QSH effect at experimentally accessible temperatures. Besides, based on the 26 Dirac fermion systems, we find a correlation between the number of Dirac points without SOC and the resultant QSH phase. We hope our findings contribute to new prospects for the design of topological materials with desired properties. |
Thursday, March 5, 2020 1:27PM - 1:39PM |
S43.00010: A first principle study on the role of Li intercalation in the structural transition from a few-layer black to blue phosphorene Md Rajib khan Musa, Ming Yu A systematic study on the role of Li intercalation played in the structure transition from a few-layer black to blue phosphorene has been carried out from first principle calculations based on the density functional theory. It is found that, depending on Li concentration and configuration intercalated on black phosphorene surface, the structure of the black phosphorous is either maintained its A17 symmetry, transferred to blue phosphorene with A7 symmetry, or distorted to form zigzag chains. Specifically, it was found that within a certain Li configurations intercalated on black phosphorene, Li atoms could play as ‘catalysts’ to drive the specific P atoms moving along specific directions, resulting bond breaking and forming, and subsequently, transforming a few-layer black to a few-layer blue phosphorene. This study opened a new pathway that, at a certain high rate Li intercalation, a feasible transition pathway from black to blue phosphorene. The role of the Li intercalation induced phase transition will be further studied and discussed, which will guide us to identify the specific conditions for such structural transformation. |
Thursday, March 5, 2020 1:39PM - 1:51PM |
S43.00011: The role of Configurational entropy in real time mass sensing. Sudeep Adhikari, Kevin Stuart David Beach We present a theoretical framework for determining the mass de- posited on a mechanical resonator subject to a flux of incoming particles of a single species. We consider the specific example of a vibrating nanostring and infer the history of mass deposition events from the frequency shifts in real time using a numerical optimization algorithm that correctly compensates for the configurational entropy. Our approach is tested against simulated data and is shown to perform well. We extend this model for a two particle system and try to comment on its applicability over a multi-particle deposition. |
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S43.00012: A Computational Study of Layered Sulfides for CO2 Reduction Photocatalysts Hao Yu, Elizabeth A Peterson, Jeffrey B Neaton The CO2 reduction reaction (CO2RR) is central to artificial photosynthesis, a means of using excess CO2 in atmosphere to generate solar fuels. While advances have been made in improving efficiency and selectivity of known catalysts for CO2RR, new materials are needed to realize scalable platforms for solar fuels generation. The high valence bands seen in low-band gap layered sulfides show promise for meeting the high redox potentials required for CO2RR, and motivate a focused high-throughput search with first-principles density functional theory (DFT). Our calculations, using van der Waals (vdW) dispersion corrections, lead to nearly a dozen photocatalyst candidates, many which are not identified by prior studies. Refining Materials Project crystal structures with vdW corrections, we find excellent agreement with experimental lattice parameters for our candidate photocatalysts. For the identified materials, we perform HSE06 band edge calculations. The alignment of the band edges with CO2RR potentials and implications for experiments on the newly identified layered sulfide compounds are discussed. |
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S43.00013: Stabilized Penta-silicene: An Elemental Ferroelectric Material with High Curie Temperature Yaguang Guo, Qian Wang The compatibility of Si semiconductor technology with current electronic devices has led to continuing search for new Si-based materials with novel properties. The recent synthesis of penta-Si nanoribbons is a new addition to this family. However, penta-silicene, a two dimensional (2D) sheet composed of only Si pentagons, was found to be unstable in penta-graphene-like configuration. Using first-principles calculations and a thorough analysis of its imaginary frequencies, we show that penta-silicene can be made dynamically stable by tilting the Si dimers to reduce the Coulomb repulsion between them. The consequence of this tilting leads to an interesting discovery: the stabilized penta-silicene breaks the centrosymmetry, resulting in intrinsic ferroelecticity with a high Curie temperature of 1190 K. This realizes the spontaneous electrical polarization in a pure 2D Si system, which has the potential to work as a future non-volatile phase change material. |
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