Zr-Be二元体系金属间化合物结构、电子、力学和热力学性能的第一性原理研究

First-Principles Investigation on Structural,Electronic,Mechanical,and Thermodynamic Properties of Intermetallics in Zr-Be Binary System

基于密度泛函理论和广义梯度近似(GGA)方法,对Zr-Be二元合金中金属间化合物ZrBe_(2)、ZrBe_(5)、ZrBe_(13)和Zr_(2)Be_(17)的结构、电子、力学和热力学性能进行了第一性原理计算。优化后的0 K点阵参数与已有的实验结果基本一致,证明了计算的可靠性。通过计算得到的形成焓和结合能表明,所有的金属间化合物都能在0 K自发形成,其中ZrBe_(5)的合金化能力最强,ZrBe_(2)的结构稳定性最好。随后,电子态密度(DOS)也被用于了解金属间化合物的稳定性。采用应力-应变法计算了这些金属间化合物的独立弹性常数。在此基础上,利用Voigt-Reuss-Hill近似推导出了多晶材料的体模量B、剪切模量G、杨氏模量E、泊松比ν和各向异性A等力学参数。此外,利用Pugh准则、泊松比和柯西压力对金属间化合物的延性行为进行了分析。在热力学性能方面,除了利用准调和近似(QHA)计算晶格振动能量、体模、热膨胀系数和比热随温度变化外,所有的声子色散曲线都说明了这些金属间化合物的动态稳定性。

The first-principles theory calculation was used to investigate the structural,electronic,mechanical,and thermodynamic properties of intermetallics ZrBe_(2),ZrBe_(5),ZrBe_(13),and Zr_(2)Be_(17) in Zr-Be binary alloy system,based on the density functional theory with generalized gradient approximation(GGA)approach.Results show that the optimized lattice parameters at 0 K are in agreement with the available experimental results,indicating the calculation reliability.The calculated formation enthalpy and cohesive energy indicate that all the intermetallics are formed spontaneously at 0 K,among which ZrBe_(5) has the strongest alloying ability and ZrBe_(2) has the best structural stability.Subsequently,the electronic density of states(DOS)was also used to investigate the intermetallic stability.The stress-strain method was adopted to calculate the independent elastic constants of the intermetallic.Based on that,the mechanical parameters of polycrystal,such as bulk modulus B,shear modulus G,Young's modulus E,Poisson's ratioν,and anisotropy value A can be deduced by Voigt-Reuss-Hill approximation.In addition,according to Pugh's criterion,Poisson's ratio,and Cauchy pressure,the ductile behavior of intermetallic was analyzed.As for the thermodynamic properties,all the phonon dispersion curves illustrate the dynamic stability of the intermetallic,and the lattice vibration energy,bulk modulus,thermal expansion coefficient,and specific heat varying with temperature change were calculated by the quasi-harmonic approximation(QHA).