PHASE NUCLEATION OF ELASTIC DEFECTS IN CRYSTALS UNDERGOING A PHASE-TRANSITION

General properties of nucleation of elastic defects in crystals underg oing a phase transition are described in the framework of a Landau-typ e approach. For static defects the phase diagram topology of a nucleus is shown to be independent of the nature and geometry of the defects and may contain additional phases which are unstable in the bulk. For moving defects the nuclei have a specific configuration and arise only below a critical speed of the defects.