CAJ | 학술논문

采用基于密度泛函理论的第一性原理赝势方法优化Mg-Er合金体系中MgEr、Mg2Er和Mg24Er5这3种金属间化合物的结构模型，通过形成热、结合能和电子结构的计算分析了化合物的稳定性与其晶体结构的内在联系。结果表明：3种Mg-Er金属间化合物的形成热和结合能均为负值，化合物的形成能力和稳定性均随着化合物中Er含量的降低而降低。在费米能级低能级区域，Mg的3s、2p轨道与Er的4f、5d轨道发生重叠，产生了轨道杂化；在费米能级高能级区域，Mg的2p轨道与Er的5d轨道也存在少量的杂化。随着化合物中Er含量的降低，化合物中平均每个原子在费米能级低能级处的成键电子数减少，化合物的稳定性降低。在Mg、Er原子周围均有大量的电荷存在，呈典型的金属键特征，Mg、Er 之间的电子云只有部分重叠，交界处电荷的畸变不大。Mg-Er金属间化合物的价键结合具有金属键和共价键两重性，其中金属键占主导地位。Mg、Er 原子的电荷转移量随化合物中Er含量降低而减少，化合物的共价键性降低，稳定性下降。
채용기우밀도범함이론적제일성원리안세방법우화Mg-Er합금체계중MgEr、Mg2Er화Mg24Er5저3충금속간화합물적결구모형，통과형성열、결합능화전자결구적계산분석료화합물적은정성여기정체결구적내재련계。결과표명：3충Mg-Er금속간화합물적형성열화결합능균위부치，화합물적형성능력화은정성균수착화합물중Er함량적강저이강저。재비미능급저능급구역，Mg적3s、2p궤도여Er적4f、5d궤도발생중첩，산생료궤도잡화；재비미능급고능급구역，Mg적2p궤도여Er적5d궤도야존재소량적잡화。수착화합물중Er함량적강저，화합물중평균매개원자재비미능급저능급처적성건전자수감소，화합물적은정성강저。재Mg、Er원자주위균유대량적전하존재，정전형적금속건특정，Mg、Er 지간적전자운지유부분중첩，교계처전하적기변불대。Mg-Er금속간화합물적개건결합구유금속건화공개건량중성，기중금속건점주도지위。Mg、Er 원자적전하전이량수화합물중Er함량강저이감소，화합물적공개건성강저，은정성하강。
Using the first-principle pseudopotential plane wave (PPW) method based on the density functional theory, structural optimization was conducted on MgEr, Mg2Er and Mg24Er5 intermetallic compounds of the binary Mg-Er alloys, and the internal relations of the stability and crystal structure of the Mg-Er intermetallic compounds were analyzed by calculating the formation heat, binding energy and electronic structure. The results show that in Mg-Er alloys, the formation heat and binding energy of three intermetallic compounds are all negative, and the alloying ability and structural stability of Mg-Er compounds are in decline with decreasing the content of Er. In low-energy region of Fermi level, the energy band is mainly dominated by hybridization of 4f and 5d orbits of Er with the 2p and 3s orbits of Mg, while in high-energy region of the Fermi level, those bonds are mainly contributed by electrons of 5d orbits of Er and 2p orbits of Mg. As the Er content decreases, the average quantities of bonding electron of each atom in low-energy region of Fermi level drops, which results in the weakened interaction among valence electrons and the reduced stability. There are a large number of charges around Mg and Er, suggesting the characteristics of typical metal bond. Meanwhile, Mg and Er share some charges to form covalent bond, while the distortion of the charge at the junction is little. Therefore, the valence bond of Mg-Er intermetallic compound has a characteristic of the duality wherein the metal bond predominates. With decreasing the Er content, the amount of charge transfer between Mg and Er atoms reduces gradually, which leads to the decrement of the proportion of covalent bond and the structural stability.