Nb掺杂对Mo_(2)FeB_(2)弹性、硬度和电子结构影响的第一性原理计算

Effect of Nb doping on the elastic properties,hardness and electronic structure of Mo_(2)FeB_(2)from first⁃principles calculations

Mo_(2)FeB_(2)具有耐高温、耐磨、高强度,是一种良好的硼基金属陶瓷材料,在模具领域有很广阔的应用前景.本文采用第一性原理计算的方法,研究了Nb元素掺杂Mo_(2)FeB_(2)合金的结构稳定性、弹性、硬度和电子结构.结合能和生成焓的计算结果表明,Nb在Mo_(2)FeB_(2)中更容易占据Fe位置,并且在Fe位掺Nb的Mo_(2)FeB_(2)比在Mo位处掺Nb具有更好的力学性能.此外,计算结果还表明,Nb掺杂可以提高Mo_(2)FeB_(2)的剪切模量、杨氏模量、体积模量和硬度,但塑性略有下降,合适的掺杂浓度应为2.5 at.%.电子结构计算结果表明,Nb掺杂Mo_(2)FeB_(2)力学性能的提高可归因于Nb-B共价键的形成.

Mo_(2)FeB_(2)is a good boron based cermet material with high temperature resistance,wear resistance and high strength.It has broad application in the field of mould.The structural stability,elastic properties,hardness and electronic structure of Mo_(2)FeB_(2)with Nb alloying were investigated by using first-principles calculations.The calculated cohesive energy and formation enthalpy showed that Nb prefers to occupy the Fe site of Mo_(2)FeB_(2),and the Nb at Fe site of Mo_(2)FeB_(2)possesses better mechanical properties compared with that at Mo site.Moreo⁃ver,the calculated results showed that Nb doping could increase the shear modulus,Young’s modulus,bulk modulus and hardness,but slightly decrease the ductility.The suitable doping concentration should be 2.5 at.%.The calculated electronic structure indicated that the increase of mechanical properties is attributed to the formation of Nb-B covalent bonds.