EFFECTS OF ALLOYING ON THE DUCTILITY OF MOSI2 SINGLE-CRYSTALS FROM FIRST-PRINCIPLES CALCULATIONS

The effects of substitutional alloying on the ductility of MoSi2 singl e crystals are studied, using first-principles total energy calculatio ns. The results are expressed in terms of a disembrittlement parameter , based on fracture mechanics theory, which characterizes brittle vers us ductile behaviour. Substitution of Mo by V, Nb, Tc and Re and subst itution of Si by Mg, Al, Ge and P was considered. The effects of subst itution of Mo by V or Nb, and substitution of Si by Mg or Al are found to be particularly beneficial to the enhancement of ductility. The ex amination of self-consistent electronic charge distributions elucidate s the changes in bonding responsible for changes in ductility.