RE2Ti3Si4(RE=Gd,Tb,Dy,Ho和Er)物理性质的第一性原理研究

Physical Properties of RE2Ti3Si4 (RE=Gd,Tb,Dy,Ho and Er) from First-principles Calculations

关键词:  第一原理计算  Ti基合金  力学性质  热力学性质

Key words:  first-principles calculations  Ti-based alloys  mechanical properties  thermodynamic properties

摘要:

[目的]对RE₂Ti₃Si₄(RE=Gd,Tb,Dy,Ho和Er)的物理性能进行研究。[方法]利用基于密度泛函的第一性原理方法对RE₂Ti₃Si₄(RE=Gd,Tb,Dy,Ho和Er)的结构性质、电子结构、力学以及热力学性质进行计算。对RE₂Ti₃Si₄单晶的弹性常数,多晶的体积模量、剪切模量和杨氏模量都进行了计算。利用准谐的德拜模型计算获得了体积模量、比热熔和热膨胀系数随着温度和压强的变化,并进行了相关的讨论。[结果]RE₂Ti₃Si₄的晶格常数计算值和实验值吻合较好。[结论]形成焓的计算值随着稀土元素原子序数的增加而呈现微小的下降趋势,这表明化合物的稳定性随着原子序数的增加而加强。电子态密度显示在费米能级之下,Ti-3d和RE-5d的态密度有着很强的杂化现象。

Abstract:

[Objective] Physical properties of the RE₂Ti₃Si₄ (RE=Gd, Tb, Dy, Ho and Er) are studied.[Methods] We present the structural, electronic structure, mechanical and thermodynamic properties of the RE₂Ti₃Si₄ (RE=Gd, Tb, Dy, Ho and Er) by using first-principles calculations based on the density functional theory (DFT).[Results] The calculated lattice constants of RE₂Ti₃Si₄ are all in good agreement with experimental data.The single crystal elastic constants of RE₂Ti₃Si₄ have been calculated, and the bulk, shear and Young's modulus are all been estimated in this work.Finally, using a quasi-harmonic Debye model, the bulk modulus, heat capacity, and coefficient of thermal expansion have also been obtained and discussed.[Conclusion] The calculated formation enthalpies of the RE₂Ti₃Si₄ show tiny decline trend with the increasing atomic number, which indicates that phase stability of RE₂Ti₃Si₄ enhance slightly with increasing atomic number.The electronic densities of states indicate that Ti-3d and RE-5d peaks show strong hybridization below the Fermi level.