(1. 中南大學(xué) 物理科學(xué)與技術(shù)學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083)
摘 要: 采用基于密度泛函理論的贗勢(shì)平面波法，計(jì)算Al-Sc的4個(gè)穩(wěn)定相的電子結(jié)構(gòu)，分析其成鍵情況，并采用基于第一性原理的熱力學(xué)計(jì)算公式，計(jì)算各相的生成焓、結(jié)合能、德拜溫度、體彈模量和自由能。結(jié)果表明：Al-Sc金屬間化合物在費(fèi)米面以下，主要通過(guò)Al 3s−Sc 3d和Al 3p−Sc 3d雜化成鍵，在費(fèi)米面以上則以Sc 3d成鍵為主；隨著Al在各相中所占比例的增大，體系中共價(jià)性增大，穩(wěn)定性提高，且Al2Sc與Al3Sc在低能級(jí)區(qū)成鍵電子較多，結(jié)構(gòu)較為穩(wěn)定。在4個(gè)化合物中，0 K時(shí)合金化形成能力最強(qiáng)的是Al2Sc(H0=−52.02 kJ/mol)，最弱的是AlSc2(H0=−35.93 kJ/mol)。自由能計(jì)算所得曲線表明：Al2Sc的結(jié)構(gòu)穩(wěn)定性最好，AlSc2的最差；隨著溫度的升高，晶體穩(wěn)定性都降低。所有熱力學(xué)計(jì)算值與試驗(yàn)值吻合良好。
關(guān)鍵字: Al-Sc金屬間化合物；電子結(jié)構(gòu)；穩(wěn)定性；熱力學(xué)性能；自由能；密度泛函理論；贗勢(shì)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
