二硼化物固溶体(Ti/Zr)1-x(Ta/Nb)xB2的结构稳定性和力学性能的第一性原理研究

Structural stability and mechanical properties of metal diborides solid solutions of (Ti/Zr)1-x(Ta/Nb)xB2 from first-principles

摘要:

通过超晶胞(SC)方法和虚拟晶体近似(VCA)方法的第一性原理计算,研究了金属二硼化物固溶体(Ti/Zr)1-x(Ta/Nb)xB2 的形(0≤x≤1)成能、混合能、晶格常数、体积、弹性常数、熔点、弹性模量、维氏硬度、断裂韧性和态密度。结果表明,二硼化物固溶体(Ti/Zr)1-x(Ta/Nb)xB2的结构稳定性随掺杂浓度的增加而降低。Ti1-x(Ta/Nb)xB2的体积随着掺杂浓度的增加而增加,这是因为Ta和Nb的原子半径大于Ti。而Zr1-x(Ta/Nb)xB2的体积逐渐变小,这归因于Ta和Nb的原子半径比Zr小。并且,二硼化物固溶体 (Ti/Zr)1-x(Ta/Nb)xB2是力学性质稳定的脆性材料。特别地是,Ta和Nb的掺杂剂可明显改善固溶体(Ti/Zr)1-x(Ta/Nb)xB2的脆性和体积模量以及断裂韧性,但硬度会降低。

Abstract:

First-principles calculations with supercell (SC) method and virtual crystal approximation (VCA) method were preformed to study the formation energy, mixing energy, lattice constant, volume, elastic constants, melting points, elastic modulus, vickers hardness, fracture toughness and density of states of (Ti/Zr)1-x(Ta/Nb)xB2 (0≤x≤1) solid solutions. The formation energy results show that the structural stability of the diboride solid solution of (Ti/Zr)1-x(Ta/Nb)xB2 decreases with the increase of the concentration of doped atoms. The volume of Ti1-x(Ta/Nb)xB2 increases with the increase of the concentration of doped atoms, because the atomic radii of Ta and Nb are larger than Ti. While the volume of Zr1-x(Ta/Nb)xB2 becomes smaller, since the atomic radius of Ta and Nb is smaller than that of Zr. Moreover, the diboride solid solution of (Ti/Zr)1-x(Ta/Nb)xB2 are mechanically stable and brittle materials. In particular, Ta and Nb dopants can significantly improve the brittleness, bulk modulus and fracture toughness of the solid solution (Ti/Zr)1-x(Ta/Nb)xB2, and reduce their vickers hardness.