Funds are provided for the continuation of the effort on high resolution transmission electron microscopy study of phase transitions and solid state reactions in modulated structures. Major emphasis of the study is directed toward understanding the mechanism of discommensuration process and the kinetics of the incommensurate-commensurate phase transitions which occur in modulated structures, in particular those formed by the CDW (charge density wave) formation in transition metal dichalcogenides such as tantalum selenide and tantalum sulfide and in long period superlattice in alloys such as silver- magnesium. Mechanisms of boundary motion in forming modulated structures of different periods which accompanies the commensuration process will also be investigated.
