(1. 中南大学 物理科学与技术学院，长沙 410083；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用基于密度泛函理论的赝势平面波法，计算Al-Sc的4个稳定相的电子结构，分析其成键情况，并采用基于第一性原理的热力学计算公式，计算各相的生成焓、结合能、德拜温度、体弹模量和自由能。结果表明：Al-Sc金属间化合物在费米面以下，主要通过Al 3s−Sc 3d和Al 3p−Sc 3d杂化成键，在费米面以上则以Sc 3d成键为主；随着Al在各相中所占比例的增大，体系中共价性增大，稳定性提高，且Al2Sc与Al3Sc在低能级区成键电子较多，结构较为稳定。在4个化合物中，0 K时合金化形成能力最强的是Al2Sc(H0=−52.02 kJ/mol)，最弱的是AlSc2(H0=−35.93 kJ/mol)。自由能计算所得曲线表明：Al2Sc的结构稳定性最好，AlSc2的最差；随着温度的升高，晶体稳定性都降低。所有热力学计算值与试验值吻合良好。
关键字: Al-Sc金属间化合物；电子结构；稳定性；热力学性能；自由能；密度泛函理论；赝势平面波法
（1. School of Physical Science and Technology, Central South University, Changsha 410083, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to calculate the electronic structures of four stable phases for Al-Sc alloys. The bonding situation was analyzed, and the formation enthalpy, binding energy, Debye temperature, bulk modulus and free energy of each phase were calculated by the thermodynamic calculation formula based on the first-principle. The results show that, under the Fermi energy, the bonds of each phase are mainly mixed by Al 3s-Sc 3d and Al 3p-Sc 3d; over the Feimi energy, those bonds are mainly contributed by electrons of Sc 3d. As the Al content increases, the covalent and stability of the system increase, and Al2Sc and Al3Sc are the stable structures by the more bonding electrons in low-energy area. Among the four crystals, the alloy-forming ability of Al2Sc(H0=−52.02 kJ/mol) is the greatest, that of the AlSc2(H0=−35.93 kJ/mol) is the lowest. The free energy curves show that the crystal stability of Al2Sc is the highest, AlSc2 is the most unstable; and the stabilities of the four crystals are all reduced with increasing temperature. All the calculations data agree well with the experimental data.
Key words: Al-Sc intermetallics compounds; electronic structure; stability; thermodynamic properties; Gibbs free energy; density functional theory; plane-wave pseudo-potential method
