The Universality of Energy Spectrum of Phonon and Vacancy Excitations in Solid Helium

• Published in: Journal of low temperature physics Vol. 149; no. 1-2; pp. 41 - 51
• Main Authors: Grigor’ev, V. N., Vekhov, Ye. O.
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.10.2007
• Subjects: Accuracy; Crystal lattices; Debye temperature; Energy spectra; Gruneisen parameter; Lattice parameters; Lattice vacancies; Low temperature physics; Mathematical models; Modulus of elasticity; Molar volume; Phonons; Solid helium; Temperature; Thermodynamic properties
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-007-9497-4

The most careful measurements on the specific heat C(T) and dP/dT (P is the pressure, T is the temperature) are analysed using a model where the thermodynamic properties of 3He and 4He crystals are described by a sum of phonon and vacancy contributions. The analysis, in which the Debye model of phonons and the Hetherington model for wide-band vacancies are used, yields a universal molar volume depence for the Debye temperature ΘD and the vacancy activation energy QV, and constant values for the Grüneisen parameters in the molar volume range of 14–24 cm3/mol. The ΘD values are found to be in good agreement with the data obtained from the elastic moduli measurements and with Horner’s theoretical calculations. The QV values are in good agreement with the X-ray measurements on the temperature dependences of 3He and 4He crystal lattice parameters analysed in terms of the Hetherington model.