(1 2 0) AND (1 2 2) Monazite Deformation Twins
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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Unusual features of 1 2 0 and 1 2 2 deformation twins in monazite monoclinic LaPO4 are described and analyzed. These features are kinks and other irregularities in 1 2 0 twins, and V-shaped indentations on 1 2 0 and 1 2 2 twin planes. Twinning shear analysis suggests that the kinks area type II deformation twin mode with shear direction n1 of 2 1 0. This complements previous analysis based on atom shuffling considerations. Shear strain compatibility requires extensive plastic deformation in the kink. The V-shaped inventions may be analogous to similar structures in b.c.c metal deformation twins. Deformation mechanisms that may be associated with these structures are discussed.