THE THEORY OF FLUCTUATIONS AND TEXTURE EMBRYOS IN STRUCTURAL PHASE-TRANSITIONS MEDIATED BY STRAIN

Structural phase transitions are considered in which the effective ord ering interaction J(R(ij)) arises from local stresses induced by the o rdering in cell i and propagated elastically to a distant cell j. The generalized Landau free energy functional is set up and four applicati ons made. Firstly the origin of metastable tweed microstructures is sh own to lie in the dense medium of strong embryonic tweed-like microdom ains existing as fluctuations at temperatures as high as 2T(c) and abo ve. Secondly the tweed-like pattern originates from the very anisotrop ic interaction associated with domain walls, and four cases are distin guished. Thirdly it is shown that the Landau-Ginzburg theory of the wi dth and shape of a domain wall can be carried over in some cases but n ot others. Fourthly the magnitude of critical fluctuations is consider ed together with corresponding corrections to the Landau theory of the phase transition in the four cases.