A dislocation tetrahedron for MoSi 2

Abstract

A tetrahedron is proposed for describing slip planes and Burgers vectors of dislocations in the tetragonal C11 b structure of MoSi 2. The faces are the four {013} slip planes; the edges are the four 1/2〈331〉 Burgers vectors plus the two 〈300〉 vectors. A combination of Greek and Roman letters is used to describe vectors and planes as for the Thompson tetrahedron. Included in the tetrahedron are the two 〈100〉, two 〈110〉 and four 1/2〈111〉 Burgers vectors, plus partial dislocations such as 1/6〈331〉, 1/4〈111〉 and 1/3〈001〉. Various dislocation reactions are described. In particular, it is shown that the 1/2〈331〉 screw dislocation should dissociate into three 1/6〈331〉 partials in an asymmetric fashion on two {013} planes. Such a configuration should have a different mobility in tension and compression. An alternative pyramid model is described which has some advantages but is less compact than the tetrahedron.