Al3M（M=Ti,Zr,Hf）亚稳相和平衡相的价电子结构分析

本文运用固体与分子经验电子理论（EET）计算了Al₃M（M=Ti,Zr,Hf）的3种晶体结构(L1₂,D0₂₂,D0₂₃)的价电子结构和最强键键能,并依此对各种结构的相稳定性及相变顺序做半定量分析.结果显示:各平衡相,即D0₂₂-A1₃Ti,D0₂₃-Al₃Zr和D0₂₂-Al₃Hf,其最强键键能分别为57.7,71.6和75.6 kJ/mol,与对应平衡相的熔点高低次序一致,确认了EET计算结果的可靠性.使用这一方法计算获得Al₃Ti,Al₃Zr和Al₃Hf的最强键键能,依此得出各亚稳相向平衡相的转变顺序与实验结果及第一性原理计算的结果相同.EET计算的最强键键能可作为评价亚稳相稳定性的一个判据.据此,由计算获得L1₂型Al₃M最强键键能推论各相的稳定性次序为Al₃Ti3 Zr3Hf,与实验所得的相稳定性次序一致,表明最强键键能作为亚稳相稳定性判据的正确性.

VALENCE ELECTRON STRUCTURE ANALYSIS OF EQUILIBRIUM AND METASTABLE PHASES OF Al3M（M=Ti,Zr,Hf）

The valence electron structure of Al₃M（M=Ti,Zr,Hf） with three crystal structures （L1₂,D0₂2,D0₂3） and the corresponding strongest bond energy（E_a） values have been calculated from the empirical electron theory（EET） of solids and molecules.Based on the calculated Ea,the stability of the phases with different structures and the sequence of phase transition have been analyzed semi-quantitatively.The results showed that,the Ea of the equilibrium phases,i.e.,D0₂₂-Al₃Ti, D0₂₃-Al₃Zr and D0₂₂-Al₃Hf,were 57.7,71.6 and 75.6 kJ/mol,respectively,which showed the same trend in magnitude with the corresponding melting point.This consistence supports the reliability of EET-based calculation results.Similarly,the E_a of Al₃Ti,Al₃Zr and Al₃Hf with three structures have been calculated and the calculated phase transition sequences are the same as the experimental results and those from first-principles calculation.The L1₂-type metastable phases of three intermetallic compounds exhibit many excellent characteristics,whereas their phase stability is crucial for application.The E_a is supposed to be a measure for the stability of metastable phase.The calculated E_a of L1₂ structure implied the phase stability in the order of Al₃Ti3Zr3Hf,which was the same as that from the transition temperatures experimentally.The E_a calculated by EET,therefore, could be a good measure for the stability of metastable phase.