Prediction of the mechanical properties of MoSi2 doped with Cr, Nb and W from first-principles calculations

摘要

The influence of Cr-, Nb- and W-doping on the mechanical properties of C11(b) MoSi2 has been investigated using first-principles calculations. Firstly, the formation enthalpies of both C11(b)- and C40-structured MoSi2 with various doping concentrations are calculated and compared, revealing that the C11(b) structure can retain good structural stability at low doping concentrations of Cr, Nb or W up to similar to 9.2 at.%. Based on the calculated elastic constants, the elastic moduli, hardness and several thermodynamic properties of doped MoSi2 have been further predicted. Cr-doping decreases the elastic moduli drastically and W-doping decreases the Debye temperature, while doping with Nb increases the B/G ratio and Poisson ratio significantly, leading to good ductility and strong metallic bonding. As revealed in the three-dimensional contours of the elastic moduli, Cr- and W-doping does not obviously affect the anisotropy of the Young's and shear moduli, but Nb-doping shows a remarkable influence. Finally, in order to clarify the doping effects, the electronic properties of doped MoSi2 are further discussed, based on the analysis of the charge density and density of states. (C) 2017 Elsevier B.V. All rights reserved.