Bi掺杂Mg_2Si的稳定性,弹性性能和电子结构的第一性原理计算

First Principles Study on Stability,Elastic Properties and Electronic Structure of Bi-Doped Mg_2Si

从动力学角度研究合金元素Bi对Mg_2Si的掺杂情况,采用CASTEP中基于密度泛函理论的第一性原理方法分析了合金元素Bi掺杂Mg_2Si的占位情况、结构稳定性、弹性性能和电子结构。计算结果表明:Mg_2Si、Mg-7Si_4Bi、Mg_8Si_3Bi均可稳定存在于体系中,Bi原子优先占据Mg_2Si晶体中Si原子位置,Mg_8Si_4Bi间隙固溶体不稳定存在体系中;Mg_Si、Mg_7Si_4Bi、Mg_8Si_3Bi均为脆性相,掺杂合金元素Bi后可以提高Mg_Si的韧性、合金化能力和导电性;Mg_2Si的成键本质是金属键、共价键和离子键的结合,Bi原子掺杂Mg2Si后产生Bi-Si和Bi-Mg键合作用,有利于提高体系的稳定性。

This paper studied the doping of Mg2Si by alloying elements Bi from the kinetic point of view.The occupancy,structural stability,elastic properties and electronic structure of alloying element Bi-doped Mg2Si phase were discussed by the first principle calculations,which was based on density functional theory in CASTEP program.The calculated results show that Mg2Si,Mg7Si4Bi and Mg8Si3Bi are stable and the interstitial solid solution Mg8Si4Bi is unstable in the system;the Bi atoms preferentially occupy the Si atoms in the Mg2Si crystal;Mg2Si,Mg7Si4Bi and Mg8Si3Bi are all brittle phase.The ductility,alloying ability and electrical conductivity of Mg2Si can be improved by doping alloying element.The essence to the bonding of Mg2Si is a combination of metal bonds,covalent bonds and ionic bonds.Bi-Si and Bi-Mg bonds are formed in Mg2Si phase by doping Bi atoms,which are beneficial to the improvement of the system stability.