A minimal model of the phonon-phason dynamics in icosahedral quasicrystals with inclusion of the pinning effect is suggested. Resonant attenuation of low-frequency acoustic waves in the temperature range corresponding to thermal activation of phasons is considered. In the long-wave length limit, the velocity of acoustic phonons is isotropic; however, the phonon-phason coupling causes anisotropy of the velocity and of the attenuation of acoustic waves with small wave vectors. These effects manifest themselves most strongly at an acoustic wave frequency close to the inverse relaxation time of phasons with the same wave vector. The pinning effect can cause a significant decrease in the anisotropy of the velocity and of attenuation of acoustic waves.

Superstructure formation is examined as a strain relaxation mechanism for polydomain structure in an "utlrathin" film on a cubic substrate. A phenomenological model of the dielectric and mechanical behavior of the ferroelectric PbTiO3 film on an MgO oxide substrate is proposed. The case of a laminar 90° domain structure with the walls tilted to 45° with respect to the film/substrate interface is considered. Taking account an inhomogeneous film–substrate coupling related to the superstructure formation and a dislocation propagation mechanism, we investigate strain relaxation and its effect on the domain structure, electrical and mechanical properties as a function of the film thickness, and temperature. It is shown that evolution of the aa-domain abundance in utlrathin film can be related to the film–substrate coupling mechanism expressed in terms of an external to the film inhomogeneous field. Its variation with the film thickness implies the existence of two distinct growth modes influencing the layer texture. For films with a thickness greater than 250 nm, aa-domains abundance is maximum and equal to 18%. For thinner films, c-domains become more stable and their proportion increases up to ~100% with the appearance of a single domain structure. Numerical modeling of electrical polarization, total strain in both domains, and mean stress in the film is performed for different thicknesses.

We have experimentally investigated the electric-field effect on the Isotropic - B2 phase transition of an achiral banana-shaped mesogen 1,3-phenyllene bis[4-(4-10-alkoxy-benoyloxy)phenyliminomethyl] (C11 compound) [1]. From microscopic observations under electric fields and measurements of the D-E hysteresis loops, the T (temperature) - E (electric field) phase diagram was established, in which a critical field is observed in the isotropic liquid. This field characterizes the first nucleation of a ferroelectric state noted BF induced by the electric field. The results are interpreted in the framework of a phenomenological model that describes the Isotropic - B2 phase transition by the condensation of a vector wave directly from the isotropic liquid [2].

We investigate the orientational order of transverse polarization vectors of long, stiff polymer molecules and their coupling to bond orientational and positional order in high density mesophases. Homogeneous ordering of transverse polarization vector promotes distortions in the hexatic phase, whereas inhomogeneous ordering precipitates crystallization of the 2D sections with different orientations of the transverse polarization vector on each molecule in the unit cell. We propose possible scenarios for going from the hexatic phase, through the distorted hexatic phase, to the crystalline phase with an orthorhombic unit cell observed experimentally for the case of DNA.