Temperature dependence of phonon frequencies in argon by inelastic neutron scattering

Vibrational properties of rare-gas solids are studied as a function of temperature and pressure by pathintegral Monte Carlo simulations with a Lennard-Jones potential model. The calculation of the static susceptibility tensor, that represents the linear response of the equilibrium system to vanishingly small forces on the atomic nuclei, leads to a nonperturbative approximation of the crystal phonons. The intrinsic anharmonicity of vibrational modes is quantified by comparison to harmonic phonon energies calculated at the equilibrium volume of the solid. Results obtained for longitudinal and transverse phonon energies at the boundary of the Brillouin zone, as well as elastic constants estimated from the propagation velocity of selected phonons, are compared to available experimental data for solid Ne and Ar. The studied temperatures cover a range from 4 K to the triple point of the rare-gas solids, while the largest studied pressures amount to about 40 kbar, that corresponds roughly to the validity limit of the employed potential model.

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“…37 We find a good agreement between the LR energies and the experimental data in the whole studied tem- perature range, as shown in Fig. 7͑b͒.…”

Section: A Temperature Dependence Of Xt and XL Phonon Energiessupporting

confidence: 76%

Anharmonic phonon energies in rare-gas solids derived by path-integral simulations

Ramı́rez

Herrero

2005

Phys. Rev. B

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“…The eigenfrequencies and eigenvectors needed for calculating Green's functions were used after fitting the dispersion curves of argon measured by Batchelder et al [17] and by Egger et al [18]. Manzhelii et al [14] have observed an enhancement in the specific heat of Ar due t o the presence of Xe impurities.…”

Section: Resultsmentioning

confidence: 99%

Specific Heat of Ar‐Xe Solid Solutions at Low Temperatures

Tiwari

1981

Physica Status Solidi (b)

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The measured specific heat of argon with solid solutions of xenon containing 5.01 and 10.88 atyo Xe are analyzed on the basis of low concentration Green's function theory. Maxima are observed a t about 4 K in the relative variation AC( T)/C( ! Z' ) of the solid mixture. The maxima are related to the appearance, in the solid mixture phonon spectrum, of quasilocal oscillations due t o introduction of heavy Xe impurity atoms into the Ar lattice. The changes in mass a t the impurity site as well as changes in the closesbneighbour force constants are taken into account in performing the computations. The force constants for the interaction between the impurity atom and its nearest neighbours are larger than the atomic interaction constants in the initial lattice. For the Ar-10.88 atyo Xe system the low-concentration theory is modified. Reasonably good agreement with the experimental data is obtained. Auf der Grundlage der Theorie Greenscher Funktionen fur niedrige Konzentrationen wird die gemessene spezifische Warme von Argon mit Festeperlosungen von Xenon mit 5,Ol und 10,88 Atyo Xe analysiert. Maxima in der relativen Anderung A C ( T ) / C ( T ) werden in der Festkorpermischung bei etwa 4 K beobachtet. Die Maxima werden dem Auftreten von quasilokalenOszillationen im Phononenspektrum der Festkorpermischung zugeordnet, die durch die Einfuhrung von schweren Xe-Storstellen in das Ar-Gitter hervorgerufen werden. Die Massenanderungen am Storstellenplatz sowie die hderungen der Kraftkonstanten der nachsten Nachbarn werden bei den Berechnungen beriicksichtigt. Die Kraftkonstanten fur die Wechselwirkung zwischen Storstellenatom und seinen niichsten Nachbarn sind groDer als die atomaren Wechselwirkungskonstanten im ursprunglichen Gitter. Fur das Ar-10,88 Atyo Xe-System wird die Theorie niedriger Konzentrationen modifizierl. Vernunftige ubereinstimmung mit den experimentellen Werten wird erhalten.

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“…(6) 22 We beleive that the approximations described in this section retain the essential physics while keeping an exploratory calculation within bounds. The potential parameters, the refractive index, and the polarizability of Ar and Xe that we used are listed in Table I.…”

Section: Theory: Computational Detailsmentioning

confidence: 99%

Two-phonon Raman scattering of light in rare gas crystals

Leese

Horton

1979

J Low Temp Phys

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In this paper we calculate the two-phonon efficiency for light scattering from rare gas crystals at all temperatures. We use a Lennard-Jones potential and.the Lorentz-Lorenz model following previous theoretical work and use the firstorder self-consistent phonon theory, supplemented by a simple model giving the phonon anharmonic widths and shifts. Our results, though larger than the experimental results, agree well with earlier calculations at 0 K and related molecular dynamics work. The calculated spectra show a rich structure that varies with temperature. We suggest that further experiments could lead to significant new insights into the nature of excitations in rare gas solids as a fimction of temperature.

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Temperature dependence of phonon frequencies in argon by inelastic neutron scattering

Cited by 26 publications

References 17 publications

Anharmonic phonon energies in rare-gas solids derived by path-integral simulations

Anharmonic phonon energies in rare-gas solids derived by path-integral simulations

Specific Heat of Ar‐Xe Solid Solutions at Low Temperatures

Two-phonon Raman scattering of light in rare gas crystals

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