The influence of substitutional alloying elements (Al, Nb and W) on the mechanical properties of MoSi2 with both C11b and C40 structures was explored by first principles calculations. Using the shear modulus/bulk modulus ratio (G/B), Poisson's ratio and Peierls stress, the change in the mechanical properties of the C40 and C11b structured MoSi2 due to the addition of the solute atom has been investigated. The results showed that the ductility of C11b MoSi2 was increased by alloying with the elements (Al and Nb) that form a C40 structured disilicide but decreased by alloying with the elements (W) that form a C11b structured disilicide. In contrast, the effect of alloying elements on the ductility of C40 MoSi2 showed a reverse trend to that of C11b MoSi2.
