scholarly journals Lattice dynamics and macroscopic properties in complex metallic alloys

2014 ◽  
Vol 70 (a1) ◽  
pp. C399-C399
Author(s):  
Pierre-François Lory ◽  
Marc de Boissieu ◽  
Peter Gille ◽  
Mark Johnson ◽  
Marek Mihalkovic ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Lattice Dynamics ◽  
Disordered Systems ◽  
Inelastic Neutron Scattering ◽  
Building Blocks ◽  
Metallic Alloys ◽  
Experimental Investigations ◽  
Icosahedral Symmetry ◽  
Macroscopic Properties ◽  
Complex Metallic Alloys

Complex metallic alloys are long-range ordered materials, characterized by large unit cells, comprising several tens to thousands of atoms [1]. These complex alloys often consist of characteristic, cluster building blocks, which in many cases show icosahedral symmetry. Numerous complex phases are known, that can be described in a rather simple way as the periodic or quasi-periodic packing of such atomic clusters. The lattice dynamics of CMAs has been the subject of both theoretical and experimental investigations in view of their interesting macroscopic properties such as low thermal conductivity. In aperiodic crystals in the higher wave-vector regime, theory predicts that the lattice modes are critical: they are neither extended as in simple crystals nor localized as in disordered systems [2]. Experimentally phonons have been studied in different CMAs systems like clathrates, approximant-crystals and quasicrystals. For all of them, acoustic modes are well-defined for wave-vectors close to Brillouin zone centres, but then broaden rapidly as the result of coupling with other excitations [3]. We will present a combined experimental and atomistic simulation study of the lattice dynamics of the complex metallic alloy Al13Co4 phase [4], which is a periodic approximant of the decagonal phase. Particular attention will be paid to the differences between the periodic and `quasiperiodic' directions. Inelastic neutron scattering measurements carried out on a large, single grain on a triple-axis spectrometer will be compared to simulations, focussing on the dispersion relations and the intensity distribution of the S(Q,ω) scattering function, which is a very sensitive test of the model [3]. Simulations are performed with DFT methods and empirical, oscillating, pair potentials [5]. In addition, thermal conductivity calculations, based on the Green-Kubo method, will be compared with measurements, which show a weak anisotropy [6-7]. In this way, the structure-dynamics-properties relation for CMAs is thoroughly explored.

Atomic Dynamics in Complex Metallic Alloys

2013 ◽  
Vol 1517 ◽  
Author(s):  
Holger Euchner ◽  
Stephane Pailhès ◽  
Tsunetomo Yamada ◽  
Ryuji Tamura ◽  
Tsutomu Ishimasa ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Structural Complexity ◽  
Building Blocks ◽  
Metallic Alloys ◽  
Strong Reduction ◽  
Large Numbers ◽  
Unit Cells ◽  
Dynamics Simulations ◽  
The Impact ◽  
Complex Metallic Alloys

ABSTRACTComplex Metallic Alloys (CMAs) are metallic solids of high structural complexity, consisting of large numbers of atoms in their unit cells. Consequences of this structural complexity are manifold and give rise to a variety of exciting physical properties. The impact that such structural complexity may have on the lattice dynamics will be discussed. The surprising dynamical flexibility of Tsai-type clusters with the symmetry breaking central tetrahedron will be addressed for Zn6Sc, while in the Ba-Ge-Ni clathrate system the dynamics of encaged Ba guest atoms in the surrounding Ge-Ni host framework is analysed with respect to the experimentally evidenced strong reduction of lattice thermal conductivity. For both systems experimental results from neutron scattering are analyzed and interpreted on atomistic scale by means of ab initio and molecular dynamics simulations, resulting in a picture with the respective structural building blocks as the origin of the peculiarities in the dynamics.

scholarly journals Uncovering design principles for amorphous-like heat conduction using two-channel lattice dynamics

2020 ◽  
Author(s):  
Riley Hanus ◽  
Janine George ◽  
Max Wood ◽  
Alexander Bonkowski ◽  
Yongqiang Cheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Dynamics ◽  
Rational Design ◽  
Amorphous Materials ◽  
Inelastic Neutron Scattering ◽  
Design Principles ◽  
Analytical Models ◽  
Phonon Modes ◽  
Gas Channel

<pre><pre>The physics of heat conduction puts practical limits on many technological fields such as energy production, storage, and conversion. It is now widely appreciated that the phonon-gas model does not describe the full vibrational spectrum in amorphous materials, since this picture likely breaks down at higher frequencies. A two-channel heat conduction model, which uses harmonic vibrational states and lattice dynamics as a basis, has recently been shown to capture both crystal-like (phonon-gas channel) and amorphous-like (diffuson channel) heat conduction. While materials design principles for the phonon-gas channel are well established, similar understanding and control of the diffuson channel is lacking. In this work, in order to uncover design principles for the diffuson channel, we study structurally-complex crystalline Yb<sub>14</sub>(Mn,Mg)Sb<sub>11</sub>, a champion thermoelectric material above 800 K, experimentally using inelastic neutron scattering and computationally using the two-channel lattice dynamical approach. Our results show that the diffuson channel indeed dominates in Yb14MgSb<sub>11</sub> above 300 K. More importantly, we demonstrate a method for the rational design of amorphous-like heat conduction by considering the energetic proximity phonon modes and modifying them through chemical means. We show that increasing (decreasing) the mass on the Sb-site decreases (increases) the energy of these modes such that there is greater (smaller) overlap with Yb-dominated modes resulting in a higher (lower) thermal conductivity. This design strategy is exactly opposite of what is expected when the phonon-gas channel and/or common analytical models for the diffuson channel are considered, since in both cases an increase in atomic mass commonly leads to a decrease in thermal conductivity. This work demonstrates how two-channel lattice dynamics can not only quantitatively predict the relative importance of the phonon-gas and diffuson channels, but also lead to rational design strategies in materials where the diffuson channel is important. </pre></pre>

scholarly journals Inelastic neutron scattering study of the lattice dynamics of the homologous compounds (PbSe)5(Bi2Se3)3m (m = 1, 2 and 3)

2018 ◽  
Vol 20 (21) ◽  
pp. 14597-14607 ◽  
Author(s):  
Selma Sassi ◽  
Christophe Candolfi ◽  
Anne Dauscher ◽  
Bertrand Lenoir ◽  
Michael Marek Koza
Keyword(s):  
Thermal Conductivity ◽  
High Resolution ◽  
Neutron Scattering ◽  
Homologous Series ◽  
Lattice Dynamics ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Homologous Compounds ◽  
Scattering Study ◽  
Neutron Scattering Study

High-resolution powder inelastic neutron scattering experiments performed on the homologous series (PbSe)5(Bi2Se3)3m (m = 1, 2 and 3) indicate that their glass-like thermal conductivity is not due to significant anharmonic behavior.

scholarly journals Lattice dynamics of the complex metallic alloys o-Al13Co4

2017 ◽  
Vol 73 (a2) ◽  
pp. C1314-C1314
Author(s):  
Marc De Boissieu ◽  
Pierre François Lory ◽  
Marek Mihalkovic ◽  
Valentina Giordanno ◽  
Peter Gille ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Metallic Alloys ◽  
Complex Metallic Alloys

scholarly journals Uncovering design principles for amorphous-like heat conduction using two-channel lattice dynamics

2020 ◽  
Author(s):  
Riley Hanus ◽  
Janine George ◽  
Max Wood ◽  
Alexander Bonkowski ◽  
Yongqiang Cheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Dynamics ◽  
Rational Design ◽  
Amorphous Materials ◽  
Inelastic Neutron Scattering ◽  
Design Principles ◽  
Analytical Models ◽  
Phonon Modes ◽  
Gas Channel

<pre><pre>The physics of heat conduction puts practical limits on many technological fields such as energy production, storage, and conversion. It is now widely appreciated that the phonon-gas model does not describe the full vibrational spectrum in amorphous materials, since this picture likely breaks down at higher frequencies. A two-channel heat conduction model, which uses harmonic vibrational states and lattice dynamics as a basis, has recently been shown to capture both crystal-like (phonon-gas channel) and amorphous-like (diffuson channel) heat conduction. While materials design principles for the phonon-gas channel are well established, similar understanding and control of the diffuson channel is lacking. In this work, in order to uncover design principles for the diffuson channel, we study structurally-complex crystalline Yb<sub>14</sub>(Mn,Mg)Sb<sub>11</sub>, a champion thermoelectric material above 800 K, experimentally using inelastic neutron scattering and computationally using the two-channel lattice dynamical approach. Our results show that the diffuson channel indeed dominates in Yb14MgSb<sub>11</sub> above 300 K. More importantly, we demonstrate a method for the rational design of amorphous-like heat conduction by considering the energetic proximity phonon modes and modifying them through chemical means. We show that increasing (decreasing) the mass on the Sb-site decreases (increases) the energy of these modes such that there is greater (smaller) overlap with Yb-dominated modes resulting in a higher (lower) thermal conductivity. This design strategy is exactly opposite of what is expected when the phonon-gas channel and/or common analytical models for the diffuson channel are considered, since in both cases an increase in atomic mass commonly leads to a decrease in thermal conductivity. This work demonstrates how two-channel lattice dynamics can not only quantitatively predict the relative importance of the phonon-gas and diffuson channels, but also lead to rational design strategies in materials where the diffuson channel is important. </pre></pre>

Complex Metallic Alloys for Applications in Magnetic Refrigeration

2015 ◽  
Vol 8 (2) ◽  
pp. 129-154
Author(s):  
Benjamin Podmiljsak ◽  
Paul J. McGuiness ◽  
Spomenka Kobe
Keyword(s):  
Magnetic Refrigeration ◽  
Metallic Alloys ◽  
Complex Metallic Alloys

scholarly journals Study of Anharmonicity in Zirconium Hydrides Using Inelastic Neutron Scattering and Ab-Initio Computer Modeling

Inorganics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 29
Author(s):  
Jiayong Zhang ◽  
Yongqiang Cheng ◽  
Alexander I. Kolesnikov ◽  
Jerry Bernholc ◽  
Wenchang Lu ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Excited States ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational States ◽  
Functional Theory ◽  
Hydrogen Deuterium ◽  
Zirconium Hydrides

The anharmonic phonon behavior in zirconium hydrides and deuterides, including ϵ-ZrH2, γ-ZrH, and γ-ZrD, has been investigated from aspects of inelastic neutron scattering (INS) and lattice dynamics calculations within the framework of density functional theory (DFT). The harmonic model failed to reproduce the spectral features observed in the experimental data, indicating the existence of anharmonicity in those materials and the necessity of further explanations. Here, we present a detailed study on the anharmonicity in zirconium hydrides/deuterides by exploring the 2D potential energy surface of hydrogen/deuterium atoms and solving the corresponding 2D single-particle Schrödinger equation to obtain the eigenfrequencies, which are then convoluted with the instrument resolution. The convoluted INS spectra qualitatively describe the anharmonic peaks in the experimental INS spectra and demonstrate that the anharmonicity originates from the deviations of hydrogen potentials from quadratic behavior in certain directions; the effects are apparent for the higher-order excited vibrational states, but small for the ground and first excited states.

scholarly journals Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Sala ◽  
M. B. Stone ◽  
Binod K. Rai ◽  
A. F. May ◽  
Pontus Laurell ◽  
...  
Keyword(s):  
Disordered Systems ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Wave Theory ◽  
Inelastic Neutron ◽  
Quantum Spin ◽  
Honeycomb Lattice ◽  
Quantum Magnetism ◽  
Van Hove Singularity ◽  
Sharp Feature

AbstractIn quantum magnets, magnetic moments fluctuate heavily and are strongly entangled with each other, a fundamental distinction from classical magnetism. Here, with inelastic neutron scattering measurements, we probe the spin correlations of the honeycomb lattice quantum magnet YbCl3. A linear spin wave theory with a single Heisenberg interaction on the honeycomb lattice, including both transverse and longitudinal channels of the neutron response, reproduces all of the key features in the spectrum. In particular, we identify a Van Hove singularity, a clearly observable sharp feature within a continuum response. The demonstration of such a Van Hove singularity in a two-magnon continuum is important as a confirmation of broadly held notions of continua in quantum magnetism and additionally because analogous features in two-spinon continua could be used to distinguish quantum spin liquids from merely disordered systems. These results establish YbCl3 as a benchmark material for quantum magnetism on the honeycomb lattice.

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