The Nature of the Glassy Phase in 4He Crystals

Antsygina, T. N.; Poltavskaya, M. I.; Chishko, K. A.

doi:10.1063/1.4929718

Cited by 5 publications

(9 citation statements)

References 23 publications

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“…To get the spectrum ( ) α ω k we solve the corresponding problem of lattice dynamics [49] within harmonic approximation with only interaction of the nearest neighbors. It is shown in [34] that hcp polytype can be interpreted as anisotropic elastic continuum with specific dispersion law in direction of disordered c axis. The averaging procedure consists in replacement of the finite differences describing interatomic interactions along c axis by spatial derivatives of corresponding order.…”

Section: T βmentioning

confidence: 99%

“…As a result, it means the passage to long-wave approximation, and such a procedure is quite natural as to the solid helium where the Debye temperature is of order higher as the melting temperature of the crystal. Finally, the phononic free energy of the 4 He polytype can be written in the form [34,35] (V is the volume of the system, a is the interatomic distance and c is the period of ideal hcp lattice, = / ) c a γ…”

Section: T βmentioning

confidence: 99%

“…As alternative to ordinary dislocation concept and glassy approach we propose [34,35] the model of hcp polytype [36][37][38] which made us possible to explain successfully the anomalies in temperature dependences of pressure reported in Refs. 1, 2.…”

Section: Introductionmentioning

confidence: 99%

“…The polytypic model makes us possible to elaborate the real physical mechanism for clarification of the unexpected thermodynamical and mechanical behavior demonstrated by the hcp solid 4 He at the low-temperature region. It is shown in [34] that hcp polytype can be interpreted as anisotropic elastic continuum with specific dispersion law in c direction due to onedimensional disorder in packing of the polytype stack. After simple averaging procedure [34] (it corresponds to the longwave approximation, which is quite natural as to the solid helium where the Debye temperature is of order higher as the melting temperature of the crystal) the system is reduced to anisotropic elastic continuum with crystallographic symmetry of hexagonal subgroup 1 3 C v (it should be emphasized that it is transversally-isotropic elastic medium).…”

Section: Introductionmentioning

confidence: 99%

“…It is shown in [34] that hcp polytype can be interpreted as anisotropic elastic continuum with specific dispersion law in c direction due to onedimensional disorder in packing of the polytype stack. After simple averaging procedure [34] (it corresponds to the longwave approximation, which is quite natural as to the solid helium where the Debye temperature is of order higher as the melting temperature of the crystal) the system is reduced to anisotropic elastic continuum with crystallographic symmetry of hexagonal subgroup 1 3 C v (it should be emphasized that it is transversally-isotropic elastic medium). The excitation of the continuum are standard phonons, but situation becomes more sophisticated if the intrinsic structure of the multilayered polytype is taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of dilute 3He–4He solid solutions with hcp structure

Chishko

2018

Low Temperature Physics

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To interpret the anomalies in heat capacity C V (T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp)4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4 He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution (with C V (T)  T 3 ) from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4 He) observed experimentally.

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Section: T βmentioning

confidence: 99%

Section: T βmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of dilute 3He–4He solid solutions with hcp structure

Chishko

2018

Low Temperature Physics

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Hexagonal Close-Packed $$^4\hbox {He}$$ 4 He as Crystalline Multilayered Polytype: An Alternative for ‘Supersolid’ or ‘Glassy-Like’ Phase

2017

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Heat capacity of xenon adsorbed on nanobundle grooves

Chishko

Соколов

2016

Low Temperature Physics

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A model of a one-dimensional nonideal gas in an external transverse force field is used to interpret the experimentally observed thermodynamic properties of xenon deposited in grooves on the surface of carbon nanobundles. A nonideal gas model with pairwise interactions is not entirely adequate for describing dense adsorbates (at low temperatures), but makes it easy to account for the exchange of particles between the 1D adsorbate and the 3D atmosphere, which is an important factor at intermediate (on the order of 35 K for xenon) and, especially, high (∼100 K) temperatures. In this paper, we examine a 1D real gas taking only the one-dimensional Lennard-Jones interaction into account, but under exact equilibrium with respect to the number of particles between the 1D adsorbate and the 3D atmosphere of the measurement cell. The low-temperature branch of the specific heat is fitted independently by an elastic chain model so as to obtain the best agreement between theory and experiment over the widest possible region, beginning at zero temperature. The gas approximation sets in after temperatures for which the phonon specific heat of the chain essentially transforms to a one-dimensional equipartition law. Here the basic parameters of both models can be chosen so that the heat capacity C(T) of the chain transforms essentially continuously into the corresponding curve for the gas approximation. Thus, it can be expected that an adequate interpretation of the real temperature dependences of the specific heat of low-dimensionality atomic adsorbates can be obtained through a reasonable combination of the phonon and gas approximations. The main parameters of the gas approximation (such as the desorption energy) obtained by fitting the theory to experiments on the specific heat of xenon correlate well with published data.

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The Nature of the Glassy Phase in 4He Crystals

Cited by 5 publications

References 23 publications

Thermodynamics of dilute 3He–4He solid solutions with hcp structure

Thermodynamics of dilute 3He–4He solid solutions with hcp structure

Hexagonal Close-Packed $$^4\hbox {He}$$ 4 He as Crystalline Multilayered Polytype: An Alternative for ‘Supersolid’ or ‘Glassy-Like’ Phase

Heat capacity of xenon adsorbed on nanobundle grooves

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