A dislocation tetrahedron for MoSi2

A tetrahedron is proposed for describing slip planes and Burgers vectors of dislocations in the tetragonal Glib structure of MoSi2. The faces are the four {013} slip planes; the edges are the four 1/2[331] Burgers Vectors plu s the two [300] vectors. A combination of Greek and Roman letters is used t o 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 vect ors, plus partial dislocations such as 1/6[331], 1/4[111] and 1/3[001]. Var ious dislocation reactions are described. In particular, it is shown that t he 1/2[331] screw dislocation should dissociate into three 1/6[331] partial s in an asymmetric fashion on two {013} planes. Such a configuration should have a different mobility in tension and compression. An alternative pyram id model is described which has some advantages but is less compact than th e tetrahedron. Published bf Elsevier Science Ltd on behalf of Acta Metallur gica Inc.