Low Temperature Physics: 34, 368 (2008); https://doi.org/10.1063/1.2911644 (9 pages)
The biatomic model of a quantum crystal
National Science Center «Kharkov Institute of Physics and Technology», 1 Akademicheskaya Str., Kharkov 61108, Ukraine
Received Octouber 27, 2007
The anharmonic zero oscillations of a crystal are considered within the framework of the diatomic model. It is shown that the amplitude of such oscillations cannot be in excess of the limiting value which is a part of the interatomic distance. The compression of a crystal decreases the amplitude of zero oscillations, while the tension increases it. It is found that the melting point of a crystal is dependent is the De Boer parameter. This dependence is qualitatively close to the observed one. It is shown that the Lindemann formula for the melting point is correct in the classic limit. There is a critical value of the De Boer parameter at which the melting point vanishes. For the De Boer parameters lower than the critical parameter, but close to it, the melting is mostly of quantum nature.
PACS: 63.20.Ry Anharmonic lattice modes;
Key words: quantum crystal, De Boer parameter, zero anharmonic oscillations, Lindemann criterion, melting point.