Planar defects and dislocations in transition-metal disilicides

The structures of transition-metal disilicides are constituted of different stacking of identical atomic planes at four different positions A, B, C, D: AB in C11b structure of e.g. MoSi2, ABC in C40 structure of e.g. VSi2 and ABDC in C54 structure of e.g. TiSi2 disilicides. In comparison with the FCC lattice with the ABC atomic plane stacking along the <111> directions, the occurrence of the fourth position, D, essentially alters the properties of defects and consequently the mechanical properties. The effect of generalized planar defects and their impacts on the dislocation core structures are discussed. In particular, we examine stacking faults and related partial dislocations on the basal planes in different types of disilicides as well as the related twin boundaries and dissociated dislocations. Our analysis of the stacking-fault-like defects is based on the calculations of γ-surfaces using ab initio methods. Predictions of possible metastable defects in all types of disilicides are reported.