The possibility of existence of nonlinear localized vibrational modes in an A 3 B two-dimensional crystal with pairwise interatomic bonds is demonstrated. Such modes are easily realized when the difference between masses of atoms A and B is significant and the spectrum of small-amplitude crystal vibrations has a sufficiently wide gap. The influence of the uniform tension/compression deformation on the small-amplitude crystal vibration spectrum and on the existence of nonlinear localized modes is investigated.
Spatiotemporal dynamics of the atmospheric kinetic energy and its components caused by the ordered and turbulent motions of air masses are estimated from minisodar measurements of three velocity vector components and their variances within the lowest 5–200 m layer of the atmosphere, with a particular emphasis on the turbulent kinetic energy. The layered structure of the total atmospheric kinetic energy has been established. From the diurnal hourly dynamics of the altitude profiles of the turbulent kinetic energy (TKE) retrieved from minisodar data, four layers are established by the character of the altitude TKE dependence, namely, the near-ground layer, the surface layer, the layer with a linear TKE increase, and the transitive layer above. In the first layer, the most significant changes of the TKE were observed in the evening hours. In the second layer, no significant changes in the TKE values were observed. A linear increase in the TKE values with altitude was observed in the third layer. In the fourth layer, the TKE slightly increased with altitude and exhibited variations during the entire observation period. The altitudes of the upper boundaries of these layers depended on the time of day. The MKE values were much less than the corresponding TKE values, they did not exceed 50 m2/s2. From two to four MKE layers were distinguished based on the character of its altitude dependence. The two-layer structures were observed in the evening and at night (under conditions of the stable atmospheric boundary layer). In the morning and daytime, the four-layer MKE structures with intermediate layers of linear increase and subsequent decrease in the MKE values were observed. Our estimates demonstrated that the TKE contribution to the total atmospheric kinetic energy considerably (by a factor of 2.5–3) exceeded the corresponding MKE contribution.
The influence of external conditions on the characteristics of long‐period structures (LPS) is considered: the temperature influence on the stabilization of the ordered structure with periodic antiphase boundaries is taken as an example. The study is carried out in terms of the phenomenological model which associates long‐period phase formation with the cooperative behaviour of atoms in planes with different types of filling. A possibility is found to form a long‐period phase in the temperature range in the vicinity of Tc. Calculations of the characteristics of the phase formed and the peculiarities of the X‐ray diffraction patterns are made. The possibility to describe the formation and behaviour of a long‐period ordered phase in terms of the same model is shown.
Using a biatomic chain of atoms as an example, whose interaction was represented by the Morse potential, we revealed a possibility for a long-lived, dynamic, long-period, nanosized state to persist in the lattice structure. This nanosized structure (in the case in question, the length of the spatial period of energy localization was found to be 16-20 nm) is generated under excitation of a vibrational short-wave mode, with the atoms of the light component only participating. The resulting dynamic nanostructures are principally different in their nature and characteristics from those described earlier and developed via a mechanism of modulation instability of short-wave vibrational modes.
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