| 第一性原理研究MgZn2相的电子结构及磁性质 |
| First-Principles Research on the Electronic and Magnetic properties of MgZn2 Phase |
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| 摘要: 运用密度泛函理论的第一性原理计算分析了MgZn2相的电子结构及相关磁性质。能带结构和态密度分析表明Zn4s和Zn4p轨道、Mg3s和Mg3p轨道分别发生sp态杂化,然后杂化态之间相互作用而形成Zn-Mg键;Mulliken布居分布计算显示:Zn1-Mg(Zn1是处于晶格边缘的Zn原子)和Zn2-Mg(Zn2是处于晶格内部的Zn原子)电子云重叠布居数接近0,电子密度分析显示Zn-Mg之间电子密度分布具有明显的定域性。结合上述结果与Zn、Mg原子的电负性差异,确定Zn-Mg键为极性共价键。分态密度(PDOS)分析显示,Zn1-Mg键和Zn2-Mg键的差异主要表现在Zn24s轨道在-10~-6eV区域对成键的贡献度高于Zn14s轨道,而Zn14s轨道在2~5eV区域对成键的贡献度高于Zn24s轨道。进一步对MgZn2的积分自旋态密度和磁矩计算表明:MgZn2磁性质表现为顺磁性,其磁性主要来源于Zn1-Mg键中的2个自旋相同的未配对电子;MgZn2的顺磁性特性将使Al-Zn-Mg-Cu(7×××系)高强铝合金产生磁致塑性效应。 |
| 关键词: MgZn2相 密度泛函理论 态密度 布居分布 磁性质 磁致塑性 |
| 基金项目: 国家自然科学基金(No.51371091,51174099)资助项目。 |
| Abstract: MgZn2 phase is the main reinforcement in the high strength-toughness aluminum alloy, such as Al-Zn-Mg-Cu (7××× series). These alloys can be strengthened by solution and aging heat treatment. The precipitation sequence is recognized as: supersaturated solute→GP area→metastable η' phase→stable η(MgZn2) phase. Therefore, it is important to know the quantum behavior and phase formation mechanism of MgZn2. But till to now, the concerned research has been rarely reported. Besides, the magnetic property of MgZn2 is also important when the aluminum alloy is processed in the presence of magnetic field. By using the first principles method, the electronic and magnetic properties of MgZn2 were calculated and analyzd in detail. The computing results on the band structure and density of state demonstrates that Zn-Mg bond is generated through the interaction of two sp hybrid state, which are from Zn4s-4p hybridized orbit and Mg3s-3p hybridized orbit separately. Especially nearby the Fermi level an intense interaction takes place between the Zn4p and Mg3p orbits. The Mulliken population distribution computation illustrates that the overlapped population distribution of Zn1-Mg or Zn2-Mg almost equals to zero. Here, it is noted that the Zn1 and Zn2 just means the Zn atoms located individually at the edge and the interior of lattice. The calculation outcome of electron density shows that the electron density distribution of Mg-Zn has an obvious locality. Combining these results with the electronegativity difference of Mg and Zn, it is regarded that the Zn-Mg is polar covalent bond. The difference of Zn1-Mg bond and Zn2-Mg bond is that the contribution of Zn24s orbit to the bond formation is higher than that of Zn14s orbit in -10~-6 eV, the contribution of Zn14s orbit to the bond formation is higher than that of Zn24s orbit in 2~5 eV. The population distribution also demonstrates that the overlapped population of Zn1-Zn1 is -1.15, which proves that the electrons are in the antibonding orbit; nevertheless, the population distribution of Zn2-Zn2 is 1.08 and the corresponding electrons are in the bonding orbital. The population distribution and electron density calculating results reveal that the Mg-Mg bond is covalent bond while the Zn1-Zn2 bond is metallic bond. Furthermore, the studies on the integrated spin density of state demonstrate that the MgZn2 phase shows paramagnetism, which stems mainly from the two unpaired electrons in the Zn1-Mg bond, and the paramagnetism of MgZn2 will make a magnetoplastic effect in Al-Zn-Mg-Cu (7××× series) high strength-toughness aluminum alloy in the presence of magnetic field. |
| Keywords: MgZn2 phase density functional theory density of states population analysis magnetic property magnetoplastic effect |
| 投稿时间：2015-04-21 修订日期：2015-09-10 |
| 摘要点击次数: 1534 |
| 全文下载次数: 1655 |
| 王宏明,郑瑞,李桂荣,李沛思.第一性原理研究MgZn2相的电子结构及磁性质[J].无机化学学报,2015,31(11):2143-2151. |
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