Low Temperature Physics: 33, 635 (2007); https://doi.org/10.1063/1.2746833 (7 pages)
Fizika Nizkikh Temperatur: Volume 33, Number 8 (August 2007), p. 835-843    ( to contents , go back )

Contributions of phonon and vacancy excitations to thermodynamic properties of solid helium

Ye.O. Vekhov, V.N. Grigor'ev, V.A. Maidanov, N.P. Mikhin, V.Yu. Rubanskiy, S.P. Rubets, E.Ya. Rudavskii, A.S. Rybalko, Ye.V. Syrnikov, and V.A. Tikhiy

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: vekhov@ilt.kharkov.ua

Received November 24, 2006, revised January 5, 2007


Precise measurements of the temperature dependence of pressure were carried out on high quality crystals of 4He and 3He-4He solutions grown under constant volume conditions. The phonon and vacancy contributions to pressure were estimated within Debye`s model of phonons and the model of wide band vacancions. The other available thermodynamic data were analyzed for pure solid helium isotopes and their solutions using this approch. The Debye temperatures and vacancy activation energies have been obtained and the universal molar volume dependence of these parameters has been found for 3He, 4He and 3He-4He solutions. The corresponding Grüneisen parameters have been obtained, which appear to be independent of the molar volume.

PACS: 67.80.-s Solid helium and related quantum crystals;
PACS: 67.57.Bc Thermodynamic properties;
PACS: 67.80.Cx Structure, lattice dynamics, and sound propagation.

Key words: solid helium, solid solutions 3He-4He, phonons, vacancies, Debye temperature, vacancy activation energy, Gruneisen parameter.

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