Twinning in Incommensurate and Commensurate Structures of ReSi{sub 2-x} Alloys

TL;DRAbstract

ReSi{sub 2-x} is usually referred to as rhenium disilicide but it actually has a stoichiometry of ReSi{sub 1.75}. Also it is usually described as having the tetragonal MoSi{sub 2}C11{sub b} structure but in fact it exhibits a number of incommensurate and commensurate structures which are based on the C11{sub b} structure. Structure A has an incommensurate periodicity of 4.14a along the a axis. It has a small orthorhombic distortion (b/a {approximately}1.005) accompanied by twinning on the (110) plane and a small monoclinic distortion (b {approximately}90.2 {degree}) accompanied by twinning on the (001) plane. Structure B is also incommensurate but has a larger monoclinic angle of 107 {degree}; B appears to result from a shear transformation of A, giving rise to (001) twins. Prolonged annealing at high temperatures results in structure C which is commensurate and has planes parallel to, and exactly 4 times the spacing of, the (101) planes of the underlying C11{sub b} structure. Structur

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