1/f2 noise as a precursor of structural reconstructions near the melting point of crystalline materials with different types of chemical bonds
Abstract
Transition phenomena near the melting point (premelting effect) are fundamental processes occurring in materials with different types of chemical bonding. At T ≥ 0.8Tm, there is a fluctuating heat release. The analysis of fluctuation processes allows obtaining information about dynamic reconstructions in various subsystems and interconnections between them within the system. The purpose of this work was to study the spectral characteristics of heat fluctuations in stationary modes of premelting materials with ionic, covalent, and metallic chemical bonds (KCl, Ge, Cu, and Sb) and to determine the type of the fluctuation process using the Hurst parameter.
The spectral characteristics of heat fluctuations in stationary modes of pre-melting KCl, Ge, Cu, and Sb at T* ~ 0.9Tm were determined by wavelet analysis. This method allows analyzing the behavior of complex systems at critical points in order to identify certain correlations and development trends in them.
The study showed that in the premelting region, the frequency spectrum of heat fluctuations was characteristic of 1/f2 noise or nonlinear Brownian noise, which is a precursor of structural reconstructions during phase transitions. The type of fluctuation processes in the premelting region of KCl, Ge, Cu, and Sb was determined using the Hurst parameter (H). It was shown that in stationary modes of premelting H > 0.5. Consequently, the previous trend of the process dynamics was very likely to develop in the same direction. However, with a decrease in the energy of the chemical bond H Æ 0.5, which indicated a decrease in the stability of the system and a likely change in the development trend for the structural reconstructions in
the premelting transition region.
Thus, near the melting point, there are unstable dynamic states, which are precursors to structural changes in the system, which have certain developmental trends. This should be taken into account when calculating the stability and reliability of materials and systems
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