<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mn>10</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>V: An Einstein Solid

Caplin, A.D.; Grüner, G.; Dunlop, John B.

doi:10.1103/physrevlett.30.1138

Cited by 58 publications

(35 citation statements)

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“…In these materials, the phonon glass property is considered to come from weakly bound atoms (rattlers) exhibiting low-energy vibrational modes which scatter the heat-carrying acoustic phonons of the lattice. The precise mechanism by which a rattler scatters phonons is still the subject of research with both resonant scattering [11][12][13] and localized mode coupling 5,6,8,14,15 having been proposed. The distinction between the two mechanisms is perhaps easily understood from the simple (kinetic theory of gases) expression for thermal conductivity:…”

Section: Introductionmentioning

confidence: 99%

Novel K rattling: A new route to thermoelectric materials?

Shoko

Kearley

Peterson

et al. 2014

Journal of Applied Physics

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We have performed ab initio molecular dynamics (MD) simulations to study the alkali-metal dynamics in the Al-doped (KAl0.33W1.67O6 and RbAl0.33W1.67O6) and undoped (KW2O6 and RbW2O6) defect pyrochlore tungstates. The K atoms exhibit novel rattling dynamics in both the doped and undoped tungstates while the Rb atoms do not. The KAl0.33W1.67O6 experimental thermal conductivity curve shows an unusual depression between ~ 50 K and ~ 250 K, coinciding with two crossovers in the K dynamics: the first at ~ 50 K, from oscillatory to diffusive, and the second at ~ 250 K, from diffusive back to oscillatory. We found that the low-temperature crossover is a result of the system transitioning below the activation energy of the diffusive dynamics whereas the high-temperature crossover is driven by a complex reconstruction of the local potential around the K atoms due to the cage dynamics.This leads to a hardening of the K potential with increasing temperature. This unusual reconstruction of the potential may have important implications for the interpretation of finite-temperature dynamics based on zero-temperature potentials in similar materials. The key result is that the novel K rattling, involving local diffusion, leads to a significant reduction in the thermal conductivity. We suggest that this may open a new route in the phonon engineering of cage compounds for thermoelectric materials where the rattlers are specifically selected to reduce the lattice thermal conductivity by the mechanism of local diffusion. a)

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Section: Introductionmentioning

confidence: 99%

Novel K rattling: A new route to thermoelectric materials?

Shoko

Kearley

Peterson

et al. 2014

Journal of Applied Physics

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“…[8][9][10][11] These localized vibration modes will result in an additional Einstein-type vibration, i.e., localized harmonic vibration with a specific frequency. If one assumes that the phonon specific heat of the BMG Ni 59.5 Nb 33.6 Sn 6.9 sample is coming from both the Debye-type and Einstein-type vibration modes, the following expression can be used to model the experimental phonon specific heat:…”

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confidence: 99%

On the existence of Einstein oscillators and thermal conductivity in bulk metallic glass

Zhou

Uher

et al. 2006

Applied Physics Letters

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Low-temperature specific heat and thermal conductivity of bulk metallic glasses are measured to identify the primary vibrational modes associated with their unique structures. An Einstein-type localized vibrational mode with an Einstein temperature of 112 K is found in bulk metallic glass Ni 59.5 Nb 33.6 Sn 6.9 . This localized vibrational mode causes resonant scattering of phonons and results in the localization of phonons which leaves the phonon hopping conduction the limiting mechanism of thermal transport in bulk metallic glass Ni 59.5 Nb 33.6 Sn 6.9 at high temperature. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2234281͔The low-temperature specific heat and thermal conductivity of rapidly quenched metallic glasses had been the subjects of experimental investigations.1-3 Recently, bulk metallic glasses ͑BMGs͒ with a thickness of 1 mm or larger have been found in a number of alloy systems which usually contains three or more elements with large atomic size difference.4,5 BMGs differ from the rapidly quenched metallic glasses in the fact that a significantly slower cooling rate is required to get bulk glassy alloys. This is usually due to their strong viscosity-temperature dependence and the formation of polytetrahedral short range ordering ͑SRO͒ in undercooled alloy melts during cooling. 6 As a result, the phonon specific heat C phonon of metallic glass may not be described by the Debye model only and additional vibrational modes which are related with their unique SRO structures can exist. It is important to clarify the nature of these additional vibration modes since they not only modify the overall vibrational mode distribution but also influence the phonon thermal conductivity L of BMG. L is determined by the vibrational excitations and their mutual interactions. In this letter, we report on the existence of Einstein-type oscillators in a typical BMG and their influence on the phonon thermal conductivity.The metallic glass samples used in this study have the composition Ni 59.5 Nb 33.6 Sn 6.9 . Their synthesis and structural characterization were similar to those reported by Choi-Yim et al. 7 The specific heat measurements were carried out between 1.8 and 154 K with the heat capacity option of the physical property measurement system ͑PPMS͒ from Quantum Design. The relative error is estimated to be within 2% based on the instrument specifications. The electrical resistivity ͑͒ and thermal conductivity ͑͒ were measured from 5 to 300 K in a cryostat equipped with a copper radiation shield. We employed a longitudinal steady-state method and used Au-0.07 at. % Fe-Chromel thermocouples. The absolute accuracy of the measurement is limited to about ±5% by the uncertainty in the thermocouple junction separation.Magnetization measurements show that BMG Ni 59.5 Nb 33.6 Sn 6.9 is paramagnetic from 300 to 1.8 K with the susceptibility of 1.28ϫ 10 −6 emu/ ͑g Oe͒. There is no magnetic contribution to C P at zero magnetic field. Therefore, C P is the sum of two terms: electronic specific heat C electron and p...

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“…In both structures we found an enhanced charge density along the Al-(V,Ti) bonds, a characteristic feature of covalent bonding. A strong directional bonding has been suggested also by NMR studies [16][17][18][19] of Al 3 V and the structural analysis: short Al-V distances [20] indicate that the bonding may have a covalent character. The COOP (Crystal Orbital Overlap Population) analysis [21] reveals that the bonds in Al 3 V are more saturated and stronger than the corresponding bonds in Al 3 Ti (because of a higher d-band filling) and the high symmetry of the transition-metal sites in the L1 2 structure leads to higher metalicity of alloys assuming this structure.…”

Section: To Cite This Versionmentioning

confidence: 93%

Interatomic bonds and the tensile anisotropy of trialuminides in the elastic limit: a density functional study for Al₃(Sc, Ti, V, Cr)

Jahnátek

Krajčı́

Hafner

2007

Philosophical Magazine

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Al10V: An Einstein Solid

Cited by 58 publications

References 4 publications

Novel K rattling: A new route to thermoelectric materials?

Novel K rattling: A new route to thermoelectric materials?

On the existence of Einstein oscillators and thermal conductivity in bulk metallic glass

Interatomic bonds and the tensile anisotropy of trialuminides in the elastic limit: a density functional study for Al₃(Sc, Ti, V, Cr)

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Al10V: An Einstein Solid

Cited by 58 publications

References 4 publications

Novel K rattling: A new route to thermoelectric materials?

Novel K rattling: A new route to thermoelectric materials?

On the existence of Einstein oscillators and thermal conductivity in bulk metallic glass

Interatomic bonds and the tensile anisotropy of trialuminides in the elastic limit: a density functional study for Al3(Sc, Ti, V, Cr)

Contact Info

Product

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Interatomic bonds and the tensile anisotropy of trialuminides in the elastic limit: a density functional study for Al₃(Sc, Ti, V, Cr)