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Proceedings Paper

Dynamics and thermodynamics of quantum crystals near the instability point in the self-consistent phonon theory
Author(s): Cecylia Malinowska-Adamska; Piotr Sloma; Janusz Tomaszewski
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Paper Abstract

Formally one can distinguish between the thermodynamic stability conditions and the dynamical ones. These last consists are easily formulated in the self-consistent phonon theory (SCPT) base don the thermodynamic double-time Green's function method. According to it the dynamic instability temperature Ts for a simple Bravais lattice defines the temperature at which the bound crystalline state of atoms vanishes that really means that the phonon frequencies become complex at sufficiently high temperatures T<EQTs. Using the reduced second order approximation of the SCPT the dynamics of crystal lattice and the thermodynamical properties of the quantum crystal in the vicinity of the instability point are investigated. The results of calculations of the pressure dependence of the instability temperature, melting criterion, internal and free energy, free Gibbs energy gas well as selected dynamic properties obtained with the help of the generalized form of the Buckingham, the Lennard-Jones and the Morse self-consistent potentials are given and compared with experimental data of solid hcp 4He and fcc 20Ne. Comparison of the theoretical and experimental results allows us to state that the limiting temperature of the dynamical stability obtained for the above-mentioned models pair potentials always appear to be the upper estimations of the real melting temperature.

Paper Details

Date Published: 10 August 2001
PDF: 6 pages
Proc. SPIE 4412, International Conference on Solid State Crystals 2000: Growth, Characterization, and Applications of Single Crystals, (10 August 2001); doi: 10.1117/12.435818
Show Author Affiliations
Cecylia Malinowska-Adamska, Technical Univ. of Lodz (Poland)
Piotr Sloma, Technical Univ. of Lodz (Poland)
Janusz Tomaszewski, Technical Univ. of Lodz (Poland)

Published in SPIE Proceedings Vol. 4412:
International Conference on Solid State Crystals 2000: Growth, Characterization, and Applications of Single Crystals

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