Bulletin of the American Physical Society
Fall 2019 Meeting of the Ohio-Region Section and the Michigan Section of the American Association of Physics Teachers
Volume 64, Number 15
Friday–Saturday, October 11–12, 2019; Flint, Michigan
Session B01: Computational and Experimental Condensed Matter Physics |
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Chair: Ronald Tackett, Kettering University Room: Kettering University Academic Building 4309 |
Saturday, October 12, 2019 8:00AM - 8:12AM |
B01.00001: Improved optoelectronic properties in CdSexTe1-x through controlled composition and short-range order Bishal Dumre, Nathan Szymanski, Vijaya Adhikari, Indiras Khatri, Daniel Gall, Sanjay Khare We employ first principles methods based on density functional theory and beyond to study CdSexTe1-x alloys in the zincblende and wurtzite structures. From the cluster expansion formalism, we provide phase diagram showing consolute temperature of 325 K where zincblende-to-wurtzite phase boundary is found for Se concentrations of x=0.5-0.6 owing to increasing ionic character of the Cd-anion bonds. Disordered CdSexTe1-x configurations are modeled using special quasirandom structures, for which optoelectronic properties are computed with the hybrid HSE06 functional. Downward bowing in the band gap and effective hole mass of the zincblende structure is highlighted for its potential benefits in photovoltaics through increased net photocurrent. Absorption coefficient and reflectivity are also reported, showing promising results in zincblende CdSexTe1-x as indicated by substantial optical absorption throughout all Se concentrations. Lastly, we identify the presence of short-range order in CdSexTe1-x characterized by clustering among like atoms in order to minimize strain. The degree of clustering, which may be tuned by temperature, also controls the magnitude of the band gap. [Preview Abstract] |
Saturday, October 12, 2019 8:12AM - 8:24AM |
B01.00002: First principles investigation of ternary Na-V-VI2 chalcogenides and their semi-classic transport coefficients Ishan Khare, Nathan Szymanski, Richard Irving Ternary chalcogenides have been of recent investigation for applications such as solar cells and thermoelectrics. We study the structural, energetic, electronic, optical, and thermoelectric properties of nine ternary Na-V-VI2 chalcogenides, NaAB2, where A represents pnictogens As, Sb, Bi and where B represents chalcogens S, Se, Te, using first principles methods based on density functional theory and beyond. Optimized lattice parameters have been computed using the generalized gradient approximation (GGA). Phonon density of states computed at zero-temperature shows that only four compounds, NaAsS2, NaAsTe2, NaSbS2, and NaSbSe2, of the nine compounds, are dynamically stable. These layered crystal structures result in computations that show highly anisotropic electronic and optical properties. Thermoelectric properties and semi-classic transport coefficients such as Seebeck coefficient and power factor are also studied by applying Boltzmann statistics. The compounds are predicted to have promising thermoelectric properties at 300 K, which indicates that these materials can be used for thermoelectric devices. Experimental verification is suggested. [Preview Abstract] |
Saturday, October 12, 2019 8:24AM - 8:36AM |
B01.00003: First principles investigation into the phase stability and enhanced hardness of TiN-ScN and TiN-YN alloys Vijaya Adhikari, Nathan Szymanski, Indiras Khatri, Daniel Gall, Sanjay Khare We study the phase stability, mechanical properties, and electronic structure of two quasi-binary ceramic systems, Ti1-xScxN and Ti1-xYxN; x=[0, 1], using first principles methods based on density functional theory, cluster expansion formalism, and Monte Carlo techniques. Owing to the similarity in ionic radii and electronegativities of their respective transition metals, strong exothermic mixing of TiN and ScN is predicted, with four ordered intermetallic phases lying on the convex hull: TiScN2, TiSc8N9, TiSc9N10, and Ti3Sc2N5 and the phase diagram reveals an upper consolute temperature of 660 K. Endothermic mixing with significant upward bowing in the formation energy at intermediate concentrations, with the consolute temperature of 7225 K is predicted from the phase diagram of Ti1-xYxN. TiN, ScN, and YN are found to display hardness values of 23.4, 25.1, and 20.6 GPa respectively. The intermetallic phase Ti3Sc2N5 is predicted to exhibit an exceptionally high hardness of 27.3 GPa. We attribute enhanced hardness to strong nitrogen p and metal d hybridization, being related to 3d eg occupation, and decreased tendency towards shearing, being related to minimal 3d t2g occupation. We suggest Ti1-xScxN alloys for implementation in hard coating applications. [Preview Abstract] |
Saturday, October 12, 2019 8:36AM - 8:48AM |
B01.00004: Stochastic Rounding of Rocks and Universal Scaling Donald Priour To probe how (and whether) initially irregular rocks become round we consider three dimensional convex stones subject to a stochastic weathering process with randomly oriented planes cumulatively removing material to mimic the erosion of rock due to collisions among stones. We find convergence to round shapes as evidenced by a systematic decrease of quantitative measures of deviations from perfectly spherical shapes. The rounding of initially angular forms occurs whether polyhedra are initially symmetric cube shapes, or irregular geometries formed by fragmenting a cube into many jagged fragments. Other more detailed gauges of departures from perfectly round shapes, such as global measures of prolateness and oblateness, also ultimately converge, albeit with the latter rising to a maximum before decaying to zero. The rounding process is governed by an acceptance probability for the area of prospective slices such that the relative mean area of new facets decreases with decreasing mass of the stone, enforcing the emergence of smooth shapes as material is carved away; we consider stones with as many as 2,500 facets. As a function of mass, we find universal dependences of observables which are independent of the scheduling of the reduction of the area of successive facets. [Preview Abstract] |
Saturday, October 12, 2019 8:48AM - 9:00AM |
B01.00005: Deposition angle, energy, and substrate temperature dependence of Cd and Te$_{\mathrm{2}}$ deposited on CdTe Indiras Khatri, Jacques Amar We study the energy, deposition angle, and substrate temperature dependence of the attachment probability and deposition site for Cd and Te$_{\mathrm{2}}$ deposited on the Cd-terminated and Te-terminated (100) and (111) surfaces of zincblende CdTe. In general, deposition on the oppositely terminated surface leads to an attachment probability which is close to 1 and relatively independent of deposition conditions, while the dominant deposition mode corresponds to growth of the next layer. In contrast, deposition on the same terminated surface leads to a significantly lower attachment probability which generally decreases with increasing deposition angle, energy, and substrate temperature. We also find that deposition on the (111) surface leads to a significant excess Te sticking probability. In contrast, the excess Te attachment probability for the (100) surface is typically significantly smaller, and in some cases may even be negative while the dominant deposition mode for same termination corresponds to joining the first layer. These results imply that even for low deposition energies and substrate temperatures, deposition on the (100) surface is likely to create interstitials in the surface layer. [Preview Abstract] |
Saturday, October 12, 2019 9:00AM - 9:12AM |
B01.00006: Micro Laser Assisted Machining of Infrared Materials Jayesh Navare, Di Kang, Charan Bodlapati, Dmytro Zaytsev, Deepak Ravindra, Hossein Shahinian This abstract, highlights the Micro Laser assisted machining ($\mu$-LAM) technology in production of optical elements made from Infrared (IR) crystals. In short, the $\mu$-LAM process is an add-on to conventional ultra-precision machining (UPM) centers, that enhances the capabilities of such machines in 2 main ways;(1) reduction of tool wear during machining and (2) enabling the fabrication of optical surfaces on very hard to machine materials. UPM's have been widely used for the past three decades in the optics manufacturing industry. The machines are very rigid and well controlled ($<$10 nm positional repeatability), and combined with using single crystal diamond tools, they are capable of producing very smooth surfaces (roughness values $<$ 5 nm RMS) on soft metals such as brass and copper. Yet, the application of UPM's is greatly limited when the work-piece material is no longer soft and ductile. The $\mu$-LAM technology uses the emission of a laser beam through the single crystal diamond tool, delivered precisely at the cutting edge. The absorbed laser power, causes a thermal "softening" of the work-piece material, thus promoting a more ductile regime of material removal. This effect, provides the opportunity to machine much harder materials using UPM's. [Preview Abstract] |
Saturday, October 12, 2019 9:12AM - 9:24AM |
B01.00007: Synthesis and Characterization of Gadolinium-Doped Magnetite Joshua Wylie, Ronald Tackett Since the emergence of magnetic fluid hyperthermia as a treatment modality for difficult to treat cancers such as glioblastoma multiformae, the need to understand the behavior of the materials involved has become paramount. Although materials like magnetite (Fe$_{\mathrm{3}}$O$_{\mathrm{4}})$ are commonly processed into ferrofluids for use in this treatment, the search for materials with higher magnetic susceptibility and heating ability drives much of the current research. The synthesis of gadolinium-doped magnetite nanoparticles via chemical co-precipitation and electrochemical deposition, and their effects on ferrofluid performance will be presented and compared. [Preview Abstract] |
Saturday, October 12, 2019 9:24AM - 9:36AM |
B01.00008: Phase transitions and associated magnetic and transport properties in Ni$_{\mathrm{2}}$Mn$_{\mathrm{0.70}}$Cu$_{\mathrm{0.25}}$Cr$_{\mathrm{0.05}}$Ga. Sunday Agbo, Khan Mahmud The need to improve the energy efficiency of temperature and climate control systems has generated a considerable research interest in magnetic refrigeration technologies. A magnetic refrigerator utilizes a particular type of magnetic materials (magnetocaloric material) as the refrigerant. Therefore, advancements in mangetic cooling technology is crucially dependent on the discovery of new materials with large tunable MCEs near room temperature. Materials that exhibit coupled magnetic and structural phase transitions with negligible thermal hysteresis, are promising in this regard. Keeping this discussion in mind, we have investigated the structural, magnetic and magnetocaloric properties Ni$_{\mathrm{2}}$Mn$_{\mathrm{0.70}}$Cu$_{\mathrm{0.25}}$Cr$_{\mathrm{0.05}}$Ga alloy using x-ray diffraction, magnetic, resistivity, and calorimetric measurements. A first order coupled magnetostructural phase transformation with a thermal hysteresis of \begin{figure}[htbp] \centerline{\includegraphics[width=0.12in,height=0.19in]{190920191.eps}} \label{fig1} \end{figure} 1 K was observed in the material near room temperature. The first-order nature of the transition was confirmed by Arrot plots. The magnetic entropy changes for a field change of 1 T to 5 T were evaluated. [Preview Abstract] |
Saturday, October 12, 2019 9:36AM - 9:48AM |
B01.00009: Shock experiments on a tabletop: a versatile technique for dynamic shock compression studies in condensed matter Mithun Bhowmick, Erin J. Nissen, Dana D. Dlott In this talk we are presenting a shock apparatus on a tabletop as a versatile technique to be applicable to shock compression experiments in condensed matter. The apparatus has already been used in recent studies of shock compression of nitromethane as well as effects of sensitizers/desensitizers on the same. The compression experiments are based on laser driven flyer plates with optical pyrometry, photon doppler velocimetry, and high-speed video photography as probes to record wavelength and time-resolved emission, simultaneous shock propagation, and real time images of the shock font. The interdisciplinary nature of the apparatus makes it useful in a myriad of applications in overlapping areas of fundamental science and device applications. [Preview Abstract] |
Saturday, October 12, 2019 9:48AM - 10:00AM |
B01.00010: Study the mechanical and magnetic properties of transition metal (M) nitrides in the cubic M4N structure using the first principle indiras Khatri, V. Adhikari, S.V. Khare We study the mechanical properties of twenty-eight transition metal (M) nitrides (TMNs) in metal-rich cubic M4N using the density functional theory [1]. We have computed lattice parameters, elastic constants, magnetic moments, formation energies, Debye temperature and Bader charge transfer. Our calculations indicate that all M4N-type nitrides except V4N, Nb4N, and Pt4N are mechanically stable. All Group 7 TMNs in the M4N structure are found to have high Vickers hardness values with the highest being 24.3 GPa for Re4N. Our computed lattice constants and magnetic dipole moments for Mn4N and Fe4N are consistent with their measured values. Spin-polarized computations reduce the hardness of some magnetic compounds like Mn4N and Fe4N. The hybridization of metal d and nitrogen 2p orbitals is found to be the key factor in determining mechanical stability and hardness in these compounds. In contrast, iconicity, as computed by Bader charge transfer, does not correlate with hardness. Our comprehensive database for binary M4N nitrides offers wide possibilities for experimental synthesis of such materials with desirable physical properties for the hard-coatings application. [1] V. Adhikari et. al., Journal of Physics and Chemistry of Solids, 120, 197, 2018 [Preview Abstract] |
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