Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session N47: Computational Design and Discovery of Novel Materials VIRecordings Available
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Sponsoring Units: DCOMP DMP Chair: Naseem Ud Din, Wayne State University Room: McCormick Place W-470B |
Wednesday, March 16, 2022 11:30AM - 11:42AM |
N47.00001: Multiferroic Properties of Polar Metallocenes Ronald E Cohen Polar metallocenes have been designed computationally with interesting atomic, electronic and magnetic structures [1]. Their properties have been studied using density functional theory with the non-local van der Waals DF2 functional. This is a challenge for current density functional codes, as accurate DF2 and magnetism with spin-orbit are required along with application of electric and magnetic fields to probe multiferroic properties. Most computations here were performed with quantum espresso, VASP, and CP2K. I will concentrate here on 5-fluoroferrocene C10H5F5Fe, predicted to be a polar antiferromagnetic and 1-azamangecene C9NH9Mn a polar ferromagnet. First-principles MD shows stability of both polar metallocenes to at least 1400K—i.e. Tc and melting are perhaps above 1400K. The Mn in 1-azamangocene is particularly interesting: computations show it to be low spin with a negative Born effective charge and static Hirshfeld charge. Experimental studies of these systems would be very exciting. |
Wednesday, March 16, 2022 11:42AM - 11:54AM |
N47.00002: Functional ABC intermetallics from first principles Konrad T Genser, Karin M Rabe Ternary ABC intermetallic compounds exhibit a rich variety of crystal structures and electronic properties. In this work, we study the structural energetics and band structures of real and hypothetical ABC intermetallic phases, primarily hexagonal and half-Heusler phases. We use first principles calculations to determine the structural parameters and the bands in each phase and the effects of strain and strain gradients on the properties and relative energies of competing phases. We connect these results to experimental measurements on known hexagonal ABC phases. The possibility of strain control and switchability of the polar distortion in polar metallic phases by strain gradients offers the promise of functional magnetic, optical, and transport properties, with examples to be discussed. |
Wednesday, March 16, 2022 11:54AM - 12:06PM Withdrawn |
N47.00003: Novel Chiral Materials for Optoelectronic and Spintronic applications. Zachary L Romestan, He Xu, Emma McCabe, Eric Bousquet, Aldo H Romero Mapping properties to symmetry principles is an ongoing and crosscutting challenge in science. Whereas structural chirality has a well known vital role in chemical and biological processes, the recent discoveries of remarkable physical properties like robust spin dependent transport due to Fermi arcs that span the Brillouin zone and significant optical activity have brought structural chirality to the forefront of materials design. Therefore, expanding the pool of chiral crystals provides ample opportunity to stimulate advances in quantum information systems and spintronics. By making chemical substitutions in the known chiral crystal LiNbZnO4, which forms an enantiomer pair in space groups 91 and 95, we have generated a family of novel spinel compounds comprised of edge connected helical sub-lattices. Here, we report the first principles characterization of the elastically and vibrationally stable unreported compounds, MgMnZnO4, MgRuZnO4 and SrMnZnO4, that host interesting giant gyrotropic dielectric response and momentum dependent spin splitting. |
Wednesday, March 16, 2022 12:06PM - 12:18PM |
N47.00004: Understanding Atomic Site Disorder in Complex Materials Ridwan Nahar, Ridwan Nahar, Sujan Budhathoki, Ka Ming Law, Casey Temple, Derek Davis, Robert Browning, Peter Powell, Gabriel Feng, Sahuj Mehta, Christian Darr, Adam Hauser Intermetallic alloys are a source of myriad emergent phenomena and promise advancements in material sciences. However, experimental realization of predicted properties has proven challenging: Atomic disorder may be inevitable when thermodynamics at the temperature of material formation allow significant swapping of constituent elements. In this work, we present our initial steps toward predicting the properties of complex materials while taking into account the frequency and effects of atomic disorder. We will present first-order density-functional theory (DFT) calculations, within the plane-wave pseudopotential and projector-augmented-wave approaches, for a series of X2YZ alloys in both full (L21) and inverse (XA) Heusler forms. To aid in understanding the frequency and property effects of X-Y site swapping, we choose Z-site elements shown experimentally to exhibit low site-swapping with X and Y sites. We will present spin polarizations, magnetic moments, density of states and band structures in the context of our obtained formation energies for each phase, making predictions of how properties of each system will change with atomic ordering in our future experimental efforts. |
Wednesday, March 16, 2022 12:18PM - 12:30PM |
N47.00005: A chemical understanding of the anomalously large bandgap of alpha-PbO Emily Oliphant, Wenhao Sun, Emmanouil Kioupakis Current intuition suggests that the band gap of binary semiconductors decreases when descending the Periodic Table. Surprisingly, α-PbO has an anomalously large bandgap of 2.4 eV compared to α-SnO at 0.7 eV. This oxide system is novel and intriguing, considering that α-SnO is the only ambipolar dopable semiconductor. While the properties of these oxides can easily be computed in DFT, there is no satisfying physical explanation for the PbO band gap increase. We use Maximally-Localized Wannier Functions to decompose the complex electronic structure into a tight-binding description, and show how the interplay of simple tight-binding parameters--such as orbital on-site energies and offsite hopping parameters --emerge into major qualitative features of the bandstructure like band position and width. Given the orbital radii and interatomic distance of GeO, SnO, PbO, our conceptual model properly rationalizes the anomalously large band gap of PbO. Briefly, the 6s orbitals of Pb exhibit Lanthanide contraction, which shifts the conduction band up and narrows its width, enlarging the band gap. Our conceptual and reductionist interpretation of the band structure may be generalizable, which would enable the intuitive navigation of other anomalous trends in semiconductor electronic structure. |
Wednesday, March 16, 2022 12:30PM - 12:42PM |
N47.00006: Crystal Features Controlling Oxygen Vacancy Formation in ABO3 Perovskites Robert B Wexler, Gopalakrishnan S Gautam, Ellen B Stechel, Emily A Carter The control of oxygen vacancy (VO) formation could unlock significant advances in perovskite metal oxide technologies including solar thermochemical fuel and electrochemical fuel/electricity production, multiferroic computer memory, and others. Despite the critical role played by VOs in determining the performance of such perovskite-oxide-based processes and devices, and the research attention they have garnered over the past few decades, an optimally simple, instructive, and efficient model for their quantitative assessment has been elusive. Here, we introduce a compact linear model for the VO formation energies of ABO3 perovskites, where A = {Ca, Sr, Ba, Ce, and La} and B = {Ti, V, Cr, Mn, Fe, Co, and Ni}, in six lattice systems (monoclinic, orthorhombic, tetragonal, rhombohedral, hexagonal, and cubic). The model takes as inputs crystal bond dissociation energies, crystal reduction potentials, band gaps, and energies above the convex hull, which can be obtained from theoretical or experimental databases. Additionally, we demonstrate that the model can be simplified, with acceptable losses in accuracy, such that only crystal bond dissociation energies and crystal reduction potentials are needed. Finally, we present our perspectives on how to improve and extend the model, which already provides both accurate and efficient predictions for high-throughput screening and an intuitive and modular phenomenology for renewable energy applications of metal oxide perovskites and beyond. |
Wednesday, March 16, 2022 12:42PM - 12:54PM |
N47.00007: Active learning and element embedding approach in neural networks for infinite-layer versus perovskite oxides Benjamin Geisler, Armin Sahinovic The observation of superconductivity in NdNiO2 films on SrTiO3(001) by Li et al. [1] has sparked considerable interest in the materials class of infinite-layer oxides. Here, we combine first-principles simulations and active learning of neural networks to explore formation energies of oxygen vacancy layers, lattice parameters, and their statistical correlations in infinite-layer versus perovskite oxides across the periodic table, and place the superconducting nickelate and cuprate families in a comprehensive context. Neural networks accurately predict these observables, which act as a fingerprint of the complex reduction reaction, using only a fraction of the data for training. Element embedding identifies chemical similarities between the individual elements in line with human knowledge. Active learning renders the training highly efficient, based on the physical concepts of entropy and information, and provides systematic accuracy control. This exemplifies how artificial intelligence may assist on the quantum scale in finding novel materials with optimized properties. [2] |
Wednesday, March 16, 2022 12:54PM - 1:06PM |
N47.00008: Rediscovering Cr2S3 as Half-semiconducting Antiferromagnet Minwoong Joe, Yisehak Gebredingle, Changgu Lee The promises of spintronics have longed for the realization of fully compensated states and full spin polarization. Half metallic/semiconducting and fully compensated materials are suggested as candidates. We use density functional theory to report that the experimentally realized rhombohedral Cr2S3 is a promising candidate as a half-semiconducting antiferromagnetic (HS-AFM) material. Our calculations demonstrate that the uniquely layered structure of Cr2S3 produces different interlayer and intralayer d-p-d hybridization schemes between Cr atoms. Strong interlayer and weak intralayer AFM coupling between different Cr sites make the overall magnetic state a fully compensated structure state. The origin of half-semiconducting and fully compensated state has been explained by a structural analysis, where magnetic exchange interaction between Cr sites is dependent on bond distance and bond angle of each Cr-centered octahedron. Furthermore, by applying strains perpendicular to the basal plane, distortion of Cr octahedron sites and Cr–Cr distance is altered, resulting in the phase transition of the material both electronically and magnetically from HS-AFM to ferrimagnetic (FiM). These studies enable us to rediscover Cr2S3 as one of ideal spintronic materials. |
Wednesday, March 16, 2022 1:06PM - 1:18PM |
N47.00009: Theoretical Investigation on the Effect of Transition-Metal Doping on Seebeck Coefficient of SiGe Alloy Tien Quang Nguyen, Ngoc Nam Ho, Katsuhiro Suzuki, Akira Masago, Hikari Shinya, Tetsuya Fukushima, Kazunori Sato To improve the efficiency of thermoelectric materials for advanced energy conversion technologies, numerous ways of modifying their electronic and structural properties have been proposed. One of the strategies is to enhance their Seebeck coefficient by impurities doping. For silicon-germanium (SiGe) alloy, the efficiency has been improved experimentally by doping iron [1]. Here, by using first-principles calculations, a systematic search is performed to investigate the effect of various transition-metals on the Seebeck coefficient of the alloy. The electronic structures of pure SiGe alloy and 3d-, 4d-, 5d-transition-metal-doped alloy systems were analyzed to compare the change in band gap energy as well as the modification of electronic density of states before and after doping. We found, among investigated transition-metals, Ti-, V-, Ru- and Os-doped SiGe alloy behave similarly to the case of Fe doping as in previous study [2]. The doping of those metals makes large improvement to the Seebeck coefficient, especially for p-type SiGe alloy in the temperature range of 300 to 900K. This enhancement is mainly attributed to the appearance of intense, sharp peaks at the bottom of conduction band contributed by the d states of transition-metals. |
Wednesday, March 16, 2022 1:18PM - 1:30PM |
N47.00010: Prediction of nontrivial band topology and superconductivity in metallic Si allotropes stable at ambient pressure Yoon-Gu Kang, In-Ho Lee, Myung Joon Han, Kee Joo Chang Silicon is one of the most abundant elements and plays a key role in modern electronic devices. Various metallic superconducting phases of Si have been reported, but most retain their crystal structure at high pressure. Thus, it remains a challenge to search for potential superconducting Si allotropes. In this work, we report the existence of both nontrivial band topology and superconductivity in three metallic Si allotropes, termed Cmcm-Si4, Cmmm-Si4, and I4/mmm-Si4. Cmcm-Si4 and I4/mmm-Si4 are newly predicted using a data-based structure search method whereas Cmmm-Si4 was proposed to be obtained by removing Li from a Cmmm-LiSi4 precursor synthesized at high pressure. These metallic allotropes exhibit superconductivity at the critical temperatures of 1.2−11.4 K. We investigate the topological characteristics of the electronic states and find the weak topological nature for all three allotropes. In particular, for Cmcm-Si4, we confirm the formation of Dirac point in the surface electronic band. Our result provides a promising platform for realizing a nontrivial band topology and superconductivity in all-Si systems at ambient pressure. |
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