Electrothermal Oscillatory Instability in Spherical Ferroelectric Resonators. Three-Mode Case

We consider the equations of interaction between electromagnetic oscillations and the temperature in a nonlinear dielectric resonator and study the dynamics of the oscillatory instability in the system. The threshold conditions (power and self-modulation frequency) of electrothermal excitation are calculated for microwave potassium-tantalate resonators for the case of three-mode interaction. The conditions for observing electrothermal excitation in the three-mode case are found to be quite favorable. In this case, the threshold power of excitation of temperature oscillations is smaller than that in the two-mode case and can amount to a few microwatts.     

Electrothermal oscillatory instability in ferroelectric resonators. Two-mode case

We consider the equations of interaction between electromagnetic oscillations and the temperature in a nonlinear dielectric resonator. The conditions for emergence of the oscillatory instability in the system are analyzed. The threshold conditions (power and automodulation frequency) of electrothermal excitation are calculated for microwave virtual-ferroelectric resonators for the simplest case of two-mode interaction. The dielectric nonlinearity is shown to impose limitations on the feasibility of electrothermal excitation. Physical Faculty, M. V. Lomonosov Moscow State University, Moscow, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 2, pp. 162–173, September 2000.     

The Gruneisen parameter for silver azide

A first-principle procedure is proposed to determine the Gruneisen parameter for a crystal by calculating the external pressure and the vibration spectrum as functions of the volume of a unit cell. In the gradient approximation of the electron density functional theory, on the basis of a linear combination of atomic orbitals, the elastic and the thermodynamic Gruneisen parameters of silver azide, which decrease with volume (with increasing pressure), are calculated with the use of the CRYSTAL09 code. The equilibrium values of the parameter γ₀ for various cold equations of state of crystals and for the thermodynamic models used are, respectively, ~2.3 and 1.6.