Katerynchuk I. Temperature-time effects in the incommensurate phases of thetramethylamin-tetrachlormetalate crystals.

The dissertation is devoted to study of the modulated structure dynamics displaying in temperature-time effects in incommensurate phase of the [N(CH3)4]2МеCl4 (Me=Cu, Zn) crystals. It has been found that when the interaction force between solitons approximates the soliton-defect interaction force the new state of incommensurate modulated structure appears. It is characterized by the few modulation waves existence in one crystallo-graphic direction. It has been established, that if "viscous" interaction appears along modulation axis, the birefringence anomalies can not be described unambiguously by the change of order parameter phase because the DDW (defect density wave) affect the joint solitons lattice motion. It has been shown that the point of appearing and disappearing of modulation wave vector determine the range of multimode state existence is accompanied by the polarized constants ellipsoid deformation as well as the optical indicatrix rotation. In condition the "viscous" interaction the dynamics of incommensurate (IC) structure in TMA-CuCl4 crystals determines though superposition of the existing modulation waves. Its time dynamics is characterized by acoustic branch of oscillation. In the TMA-CuCl4 crystals the DDW formed in IC phase saves in ferroelastic phase too. It has been established that if atom displacements are bigger the their normal oscillation the structure has wide cross-domain margins blocked by DDW resulting in peak-like behavior of the residual intensity. The electric field applied along modulation axis strengthens the interaction of defects and impurities with modulation structure. When the electric field action is described by the some irreducible representation as the spontaneous polarization then the new commensurate polar phase appears. The creation of the wave with difference value of wave vector requires energy wich discharges in crystal rebuilding process. The transition from one methastable state to another accompanied by the free energy change: the from transformation ofthe potential energy into kinetic (soliton jont motion energy). The chaotic phase has bigger amplitude values of modulating waves participating in superposition. The residual intensity in chaotic phase behaves nonmonotonously. It is caused by the contribution of optical indicatrix rotation.