Periodic anti-phases. Long distance antiphase-order transformations (1961)

Periodic anti-phases are ordered structures in which the movable elements alternates regularly between two available sites, in one or two directions. We study in the present work two particular properties of periodic anti-phases : 1- The irrationality or the continuous variation of the periodic anti-phase. 2- The reversible transition between the anti-phase state and that of long distance order. We have calculated the distribution of the diffracted amplitudes for the 'rational statistic' model. They can easily be identified and the two types of diagram observed are presented. For the long distance anti-phase-order transformation, we propose a model in which a domain grows laterally at the expense of the other. Calculation shows that in this case certain order reflections re-appear accompanied by extra satellites whose amplitude is not proportional to that of the pure anti-phase satellites, the opposite of the case of a double diffraction. The irreversible evolution of Au3Mn alloys is then described; in this case interactions between domains of different type occur. Finally a diagram for the alloy Au3Mn is given; the anti-phase boundaries are made up of 130 planes. (authors)