Mg-Y-Cu合金长周期有序相热力学稳定性及其电子结构的第一性原理研究  

First-principles study of the thermodynamic stabilities and electronic structures of long-period stacking ordered phases in Mg-Y-Cu alloys

作　　者：马振宁[1] 周全[2] 汪青杰[1] 王逊[1] 王磊[3] 

机构地区：[1]沈阳建筑大学理学院,沈阳110168 [2]南昌航空大学航空制造工程学院,南昌330063 [3]东北大学,材料各向异性与织构教育部重点实验室,沈阳110819

出　　处：《物理学报》2016年第23期186-193,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51261026)资助的课题~~

摘　　要：采用基于密度泛函的第一性原理平面波赝势方法计算了Mg-Y-Cu合金中长周期有序相14H和18R(18R(m),18R(t))的形成焓、反应能、电子态密度和电荷密度.计算结果表明,14H和18R相都具有负的形成焓,说明两相都能够由单质转变形成,并且18R相比14H相更容易形成,但14H相具有更好的热力学稳定性;14H和18R相的态密度分布形态和变化趋势相似,它们的成键峰均主要来自于Mg的3s轨道、Mg的2p轨道,Cu的3d轨道和Y的4d轨道的贡献,且在费米能级低能级区域产生了轨道杂化效应.14H相和18R相的成键都具有明显的共价性.通过对各相(0001)面的电荷密度分析表明,14H和18R相中的Cu原子和Y原子之间都形成了共价键,并且14H相的共价性比18R相的共价性更强.The long-period stacking ordered（LPSO） phases in magnesium alloys possess excellent mechanical performances,and have received considerable attention. The strengthening LPSO phases, such as 14 H and 18 R structures, are found experimentally in some Mg-Y-Cu alloys, which can significantly enhance the mechanical performances of the alloys.However,it is unknown which phase is more stable thermodynamically, and easier to form during the solidification. In this paper,thermodynamic stabilities and electronic characteristics of LPSO phases 14 H and 18R（18R（m）, 18R（t）） in Mg-Y-Cu alloys are investigated by the first-principles pseudopotential method based on the density functional theory. The present calculations are performed by using Vienna ab-initio simulation package（VASP） with projector-augmented plane wave pseudopotential, and the generalized gradient approximation is used to deal with and describe the exchange-correlation interaction. The plane wave cutoff energy is set to be 360 eV, the forces on all the atoms are less than 0.02 e V/？. The k-point meshes of Brillouin zone sampling in a primitive cell are based on the Monkhorst-Pack scheme. The calculated enthalpies of formation indicate that the 14 H and 18 R phases coexist in Mg-Y-Cu alloys. The 18 R phase has a larger absolute value of formation enthalpy, which means that it is easier to form than the 14 H phase. The reaction energy is also computed for the transformation from the 18 R phase to 14 H phase, which shows that the 14 H phase is more stable than the 18 R phase. The results for density of states（DOS） reveal that the bondings of the 14 H and 18 R phases occur mainly among the valence electrons of Cu 3d, Y 4d, Mg 3s and Mg 2p orbits while those of Cu 4s, Y 4s and Y 4p orbits are very weak in the whole region. The bonding peaks of the 14 H, 18R（m）, and 18R（t） phases are localized, and the corresponding hybridization orbits, which are all or part of Mg 3s, Mg 2p, Cu 3d and Y 4d orbits, are determined. At the same time, th

关 键 词：Mg-Y-Cu合金 长周期有序相 第一性原理 电子结构 

分 类 号：O469[理学—凝聚态物理]