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Full-Text Articles in Physics

Complex Oscillatory Decrease With Size In Diffusivity Of {100}-Epitaxially Supported 3d Fcc Metal Nanoclusters, King C. Lai, James W. Evans Oct 2019

Complex Oscillatory Decrease With Size In Diffusivity Of {100}-Epitaxially Supported 3d Fcc Metal Nanoclusters, King C. Lai, James W. Evans

James W. Evans

Diffusion and coalescence of supported 3D metal nanoclusters (NCs) leads to Smoluchowski Ripening (SR), a key pathway for catalyst degradation. Variation of the NC diffusion coefficient, DN, with size N (in atoms) controls SR kinetics. Traditionally, a form DN ∼ N−β was assumed consistent with mean-field analysis. However, KMC simulation of a stochastic model for diffusion of {100}-epitaxially supported fcc NCs mediated by surface diffusion reveals instead a complex oscillatory decrease of DN with N. Barriers for surface diffusion of metal atoms across and between facets, along step edges, etc., in this model are selected to accurately capture behavior ...


Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney Oct 2019

Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney

A. I. Goldman

Whereas magnetic frustration is typically associated with local-moment magnets in special geometric arrangements, here we show that SrCo2As2 is a candidate for frustrated itinerant magnetism. Using inelastic neutron scattering (INS), we find that antiferromagnetic (AF) spin fluctuations develop in the square Co layers of SrCo2As2 below T approximate to 100 K centered at the stripe-type AF propagation vector of (1/2, 1/2), and that their development is concomitant with a suppression of the uniform magnetic susceptibility determined via magnetization measurements. We interpret this switch in spectral weight as signaling a temperature-induced crossover from an instability toward ferromagnetism ordering to ...


Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney Oct 2019

Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney

Peter P. Orth

Whereas magnetic frustration is typically associated with local-moment magnets in special geometric arrangements, here we show that SrCo2As2 is a candidate for frustrated itinerant magnetism. Using inelastic neutron scattering (INS), we find that antiferromagnetic (AF) spin fluctuations develop in the square Co layers of SrCo2As2 below T approximate to 100 K centered at the stripe-type AF propagation vector of (1/2, 1/2), and that their development is concomitant with a suppression of the uniform magnetic susceptibility determined via magnetization measurements. We interpret this switch in spectral weight as signaling a temperature-induced crossover from an instability toward ferromagnetism ordering to ...


Uncompensated Polarization In Incommensurate Modulations Of Perovskite Antiferroelectrics, Tao Ma, Zhongming Fan, Bin Xu, Tae-Hoon Kim, Ping Lu, Laurent Bellaiche, Matthew J. Kramer, Xiaoli Tan, Lin Zhou Sep 2019

Uncompensated Polarization In Incommensurate Modulations Of Perovskite Antiferroelectrics, Tao Ma, Zhongming Fan, Bin Xu, Tae-Hoon Kim, Ping Lu, Laurent Bellaiche, Matthew J. Kramer, Xiaoli Tan, Lin Zhou

Xiaoli Tan

Complex polar structures of incommensurate modulations (ICMs) are revealed in chemically modified PbZrO3 perovskite antiferroelectrics using advanced transmission electron microscopy techniques. The Pb-cation displacements, previously assumed to arrange in a fully-compensated antiparallel fashion, are found to be either antiparallel but with different magnitudes, or in a nearly orthogonal arrangement in adjacent stripes in the ICMs. Ab initio calculations corroborate the low-energy state of these arrangements. Our discovery corrects the atomic understanding of ICMs in PbZrO3-based perovskite antiferroelectrics.


Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi Aug 2019

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi

Valery I. Levitas

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise ...


Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho Aug 2019

Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho

Ralph E. Napolitano

The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. We focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. Our results show that a Bergman-type motif ...


A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano Aug 2019

A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano

Ralph E. Napolitano

Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general ...


Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender Aug 2019

Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender

Thomas A. Lograsso

We report magnetic force microscopy (MFM) measurements on the iron-based superconductor Ba1−xKxFe2As2. By measuring locally the Meissner repulsion with the magnetic MFM tip, we determine the absolute value of the in-plane magnetic penetration depth (λab) in underdoped, optimally doped, and overdoped samples. The results suggest an abrupt increase of λab as doping is increased from xopt, which is potentially related to the presence of a quantum critical point. The response of superconducting vortices to magnetic forces exerted by the MFM tip for x=0.19 and 0.58 is compatible with previously observed structural symmetries at those doping levels.


Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston Jul 2019

Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston

Duane D. Johnson

Electron-doped Sr(Co{1-x}Ni{x})2As2 single crystals with compositions x = 0 to 0.9 were grown out of self-flux and SrNi2As2 single crystals out of Bi flux. The crystals were characterized using single-crystal x-ray diffraction (XRD), magnetic susceptibility chi(H,T), isothermal magnetization M(H,T), heat capacity Cp(H,T), and electrical resistivity ho(H,T) measurements versus applied magnetic field H and temperature T. The chi(T) data show that the crystals exhibit an antiferromagnetic (AFM) ground state almost immediately upon Ni doping on the Co site. Ab-initio electronic-structure calculations for x = 0 and x = 0 ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield Jul 2019

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Paul C. Canfield

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield Jul 2019

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Paul C. Canfield

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee Jul 2019

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Paul C. Canfield

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Lack Of Superconductivity In The Phase Diagram Of Single-Crystalline Eu(Fe1-Xcox)(2)As-2 Grown By Transition Metal Arsenide Flux, Gang Wang, William R. Meier, Warren E. Straszheim, Joshua Slagle, Sergey L. Bud’Ko, Paul C. Canfield Jul 2019

Lack Of Superconductivity In The Phase Diagram Of Single-Crystalline Eu(Fe1-Xcox)(2)As-2 Grown By Transition Metal Arsenide Flux, Gang Wang, William R. Meier, Warren E. Straszheim, Joshua Slagle, Sergey L. Bud’Ko, Paul C. Canfield

Paul C. Canfield

The interplay of magnetism and superconductivity (SC) has been a focus of interest in condensed matter physics for decades. EuF e 2 A s 2 has been identified as a potential platform to investigate interactions between structural, magnetic, and electronic effects as well as the coexistence of magnetism and SC with similar transition temperatures. However, there are obvious inconsistencies in the reported phase diagrams of Eu ( F e 1 − x C o x ) 2 A s 2 crystals grown by different methods. For transition metal arsenide (TMA)-flux-grown crystals, even the existence of SC is uncertain. Here we reexamine the ...


Is It Possible To Stabilize The 1144-Phase Pnictides With Tri-Valence Cations?, Boqun Song, Manh Cuong Nguyen, Cai-Zhuang Wang, Paul C. Canfield, Kai-Ming Ho Jul 2019

Is It Possible To Stabilize The 1144-Phase Pnictides With Tri-Valence Cations?, Boqun Song, Manh Cuong Nguyen, Cai-Zhuang Wang, Paul C. Canfield, Kai-Ming Ho

Paul C. Canfield

A lately discovered 1144 phase has generated significant interest for its high superconducting temperatures, disorder-free doping, and various chemical substitutions. However, it has only been found in iron arsenides ( A B Fe 4 As 4 ), and cations are limited to +1 or +2 valence states (e.g., alkali metals, alkaline earth elements, and Eu). Whether more 1144 phases could be stabilized and whether intriguing properties exist are questions of general interest. In this work, we investigate 1144 iron and cobalt arsenides with tri-valence cations (La, Y, In, Tl, Sm, Gd). We study phase stability among other competing phases: 122 solution ...


Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam Jul 2019

Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam

Duane D. Johnson

Magnesium silicides are favorable thermoelectric materials considering resource abundance and cost. Chromium (Cr) doping in magnesium silicides has not yet been explored. Using first-principles calculations, we have studied the stability of Mg2Si with chromium (1.85, 3.7, 5.55, and 6.25% Cr) and tin (12.5 and 50% Sn). Three Mg2Si compounds doped with Sn, (Sn + Bi), and (Sn + Bi + Cr) are used to explain doping effects on thermoelectric performance. Notably, Cr behaves nonmagnetically for ≤2%Cr, after which ferromagnetic ordering is favored (≤12.96% Cr), despite its elemental antiferromagnetic state. With alloying of Sn (70.4%), Mg2Si ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

Deborah L. Schlagel

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

A. I. Goldman

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

Thomas A. Lograsso

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan Jun 2019

Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan

Xiaoli Tan

The antiferroelectric-ferroelectric phase transition in PbZrO3-based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is ...


Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk Jun 2019

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk

Paul C. Canfield

To reduce material and processing costs of commercial permanent magnets and to attempt to fill the empty niche of energy products, 10–20 MGOe, between low-flux (ferrites, alnico) and high-flux (Nd2Fe14B- and SmCo5-type) magnets, we report the synthesis, structure, magnetic properties, and modeling of Ta-, Cu-, and Fe-substituted CeCo5. Using a self-flux technique, we grow single crystals of Ce15.1Ta1.0Co74.4Cu9.5, Ce16.3Ta0.6Co68.9Cu14.2, Ce15.7Ta0.6Co67.8Cu15.9, Ce16.3Ta0.3Co61.7Cu21.7, and Ce14.3Ta1.0Co62.0Fe12.3Cu10.4. X-ray-diffraction analysis shows that these materials retain a CaCu5 substructure and incorporate small amounts of ...


Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley Jun 2019

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley

Duane D. Johnson

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the ...


A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox Jun 2019

A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox

Alberto Passalacqua

A computational algorithm for polydisperse bubbly flow is developed by combining quadrature-based moment methods (QBMM) with an existing two-fluid solver for gas–liquid flows. Care is taken to ensure that the two-fluid model equations are hyperbolic by generalizing the kinetic model for the bubble phase proposed by Bieseuvel and Gorissen (1990). The kinetic formulation for the bubble phase includes the full suite of interphase momentum exchange terms for bubbly flow, as well as ad hoc bubble–bubble interaction terms to model the transition from isolated bubbles to regions of pure air at very high bubble-phase volume fractions. A robust numerical ...


A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox Jun 2019

A Quadrature-Based Moment Method For Polydisperse Bubbly Flows, Jeffrey C. Heylmun, Bo Kong, Alberto Passalacqua, Rodney O. Fox

Rodney O. Fox

A computational algorithm for polydisperse bubbly flow is developed by combining quadrature-based moment methods (QBMM) with an existing two-fluid solver for gas–liquid flows. Care is taken to ensure that the two-fluid model equations are hyperbolic by generalizing the kinetic model for the bubble phase proposed by Bieseuvel and Gorissen (1990). The kinetic formulation for the bubble phase includes the full suite of interphase momentum exchange terms for bubbly flow, as well as ad hoc bubble–bubble interaction terms to model the transition from isolated bubbles to regions of pure air at very high bubble-phase volume fractions. A robust numerical ...


Revealing The Nature Of Antiferroquadrupolar Ordering In Cerium Hexaboride: Ceb6, C. K. Barman, Prashant Singh, Duane Johnson, Aftab Alam Jun 2019

Revealing The Nature Of Antiferroquadrupolar Ordering In Cerium Hexaboride: Ceb6, C. K. Barman, Prashant Singh, Duane Johnson, Aftab Alam

Duane D. Johnson

The cerium hexaboride (CeB6) f-electron compound displays a rich array of low-temperature magnetic phenomena, including a “magnetically hidden” order, identified as multipolar in origin via advanced x-ray scattering. From first-principles electronic-structure results, we find that the antiferroquadrupolar(AFQ) ordering in CeB6 arises from crystal-field splitting and yields a band structure in agreement with experiments. With interactions of p electrons between Ce and B6 being small, the electronic state of CeB6 is suitably described as Ce(4f1)3+(e−)(B6)2−. The AFQ state of orbital spins is caused by an exchange interaction induced through spin-orbit interaction, which also splits the ...


Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan Jun 2019

Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan

Xiaoli Tan

(Bi 1/2Na 1/2)TiO 3-based solid solutions, one of the major systems of lead-free piezoelectric ceramics, exhibit a low thermal depolarization temperature ( T d~100°C). It was reported that by incorporating 30 mol% ZnO particles to form a ceramic composite of (Bi 1/2Na 1/2) 0.94Ba 0.06TiO 3/ZnO, the depolarization process can be shifted up to ~250 °C. In the present work, a variety of advanced transmission electron microscopy techniques, including in situ heating, annular bright-field, high-angle annular dark-field, geometric phase analysis, energy-dispersive spectrum and electron energy-loss spectroscopy, are employed to investigate the ...


Flexoelectricity In Solids Progress, Challenges, And Perspectives, Bo Wang, Yijia Gu, Shujun Zhang, Long-Qing Chen May 2019

Flexoelectricity In Solids Progress, Challenges, And Perspectives, Bo Wang, Yijia Gu, Shujun Zhang, Long-Qing Chen

Yijia Gu

The flexoelectricity describes the contribution of the linear couplings between the electric po- larization and strain gradient and between polarization gradient and strain to the thermo- dynamics of a solid and represents the amount of polarization change of a solid arising from a strain gradient. Although the magnitude of the flexoelectric effect is generally small, its con- tribution to the overall thermodynamics of a solid may become significant or even dominant at the nanometer scale. Recent experimental and computational efforts have led to significant ad- vances in our understanding of the flexoelectric effect and its exploration of potential applica- tions ...


High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian Jan 2019

High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian

Baskar Ganapathysubramanian

Visual inspections for identifying focusing points in inertial microfluidic flows are prone to misinterpreting stable locations and focusing shifts in the case of non-trivial focusing patterns. We develop and deploy an approach for automating the calculation of focusing patterns for a general channel geometry, and thereby reduce the dependence on empirical/visual procedures to confirm the presence of stable locations. We utilize concepts from interpolation theory (to represent continuous force-fields using discrete points), and stability theory to identify "basins of attraction" and quantitatively identify stable equilibrium points. Our computational experiments reveal that predicting equilibrium points accurately requires upto ×10-20 times ...


Call For Abstracts - Resrb 2019, July 8-9, Wrocław, Poland, Wojciech M. Budzianowski Dec 2018

Call For Abstracts - Resrb 2019, July 8-9, Wrocław, Poland, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.


Local Environment Of Iron And Uranium Ions In Vitrified Iron Phosphate Glasses Studied By Fe K And Uliii-Edge X-Ray Absorption Fine Structure Spectroscopy, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, D. E. Day, George Daniel Waddill, P. G. Allen, C. H. Booth, J. J. Bucher, D. L. Caulder, D. K. Shuh, M. Grimsditch, M.-L. Saboungi Sep 2018

Local Environment Of Iron And Uranium Ions In Vitrified Iron Phosphate Glasses Studied By Fe K And Uliii-Edge X-Ray Absorption Fine Structure Spectroscopy, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, D. E. Day, George Daniel Waddill, P. G. Allen, C. H. Booth, J. J. Bucher, D. L. Caulder, D. K. Shuh, M. Grimsditch, M.-L. Saboungi

Delbert E. Day

The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 - x)Fe2O3-xUO2-60P2O5 and (1-x-y)(40Fe2O3-60P2O5)-xUO2-y(Na2O or CaO) was investigated using Fe K-edge and U LIII-edge x-ray absorption fine structure spectroscopy. Replacing Fe2O3 by UO2 in the glass caused more distortion in the coordination environment of Fe(III) ions. Extended x-ray absorption fine structure fits revealed that the Fe-P bonds observed in the base ...


A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day Sep 2018

A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day

Delbert E. Day

The atomic structure of iron phosphate glasses containing uranium has been studied by complementary neutron and x-ray scattering techniques. by combining x-ray and neutron structure factors, detailed information about different pair interactions has been obtained. Most of the basic structural features such as coordination numbers and O-O and P-O distances in uranium containing glasses are the same as those in the base glass of batch composition 40Fe2O3-60P2O5 (mol %). However, the Fe-O distances change slightly with the addition of uranium. The observed structural parameters support a structural model in which the waste elements occupy voids in the Fe-O-P network, hence, not ...