中文摘要：

采用超级胞和广义梯度近似条件下投影缀加平面波的第一性原理方法研究了β相Ti搿（X=Nb，Mo）合金结构稳定、弹性性能及其电子结构，并利用Voigt—Reuss—Hill平均方法从单晶Ti-X合金的弹性常数计算出了其多晶合金的弹性模量。研究结果表明，β型Ti—Nb和Ti-Mo合金的β结构稳定性随着Nb，Mo和Ta含量的增加而增加，当Nb或Mo含量为25at％时，Ti—Nb和Ti—Mo合金表现出最低的弹性模量。进一步，利用计算出的Ti-X合金的电子态密度（DOS）分析讨论了Nb和Mo合金元素含量对这2种合金结构稳定性的影响机理。

英文摘要：

The phase stability, the elastic constant and the electronic structure of Ti-X （X=Nb, Mo） alloys having bcc structure were studied from first-principles calculations by the method of supercell and the projector augmented wave within the generalized gradient approximation. The elastic moduli of the polycrystal alloys were estimated from the elastic constants of the single crystal by the Voigt-Reuss-Hill averaging method. The results reveal that Nb and Mo contents have a significant influence on the phase stability and the elastic properties of the β type Ti-X alloys. The phase stability, the elastic constants, the elastic modulus and the shear modulus of β type Ti-X alloys increase with the X content increasing. The lowest elastic modulus of the alloys is achieved as the X content is about 25%. Moreover, the phase stability of the alloys was discussed based on the calculated density of state （DOS）.