Mechanism of phase transitions in hexagonal model K

A number of dielectric and ferroelectric crystals posses incommensurately modulated phases, which could be seen as a sequence of discommensuration planes. Using simple hexagonal microscope model the nucleation of topological defect responsible for creation of discommensuration, has been studied. Example of the collective nucleation mechanism in the commensurate 1/4→incommensurate phase transition driven by stripples will be discussed. During the phase transition from 3q two-dimensional modulated phase to 1q stripe commensurate phase formation of domain-like texture has been observed. (author). 10 refs, 2 figs