金属间化合物Al_(3)Ti多晶型性质的DFT理论研究

Theoretical Study on Al_(3)Ti Polymorphs'Properties with DFT Method

采用基于密度泛函理论(DFT)的第一性原理研究方法,考察了在DO_(22)、DO_(23)、DO_(19)和L1_(2)四种晶体结构下,Al_(3)Ti金属间化合物的热力学稳定性和力学性能。计算结果表明,四种结构的Al_(3)Ti生成焓均为负值,表明四者在热力学上均可以稳定存在。其中,DO_(23)-Al_(3)Ti的生成焓最负,热力学稳定性最高,其后依次是DO_(22)、L1_(2)、DO_(19)三种结构。力学性能计算表明,DO_(23)结构具有最高的杨氏模量E和体模量B。根据体模量B和剪切模量G的比值B/G,可知四种结构的Al_(3)Ti均呈脆性。各向异性指数A^(U)的排序为DO_(22)>DO_(23)>L1_(2)>DO_(19)。

The thermodynamic stability and mechanical properties of Al_(3)Ti intermetallic compounds with four crystal structures of DO_(22),DO_(23),DO_(19) and L1_(2) were investigated by using the first-principles method based on density functional theory(DFT).The calculation results showed that the formation enthalpies of Al_(3)Ti of the four structures were all negative,which indicated that the four structures could be thermodynamically stable.Among them,DO_(23)-Al_(3)Ti had the most negative value,which indicated it had the highest thermodynamic stability,followed by DO_(22),L1_(2) and DO_(19).The mechanical properties of DO_(23) structure showed that it had the highest Young's modulus E and bulk modulus B.According to the ratio B/G of the bulk modulus B and the shear modulus G,it could be obtained that all the Al_(3)Ti polymorphs were brittle.Their anisotropic index A^(U) could be sequenced as DO_(22)>DO_(23)>L1_(2)>DO_(19).