(CoAl)n(1≤n≤6)合金团簇结构、稳定性和磁性的第一性原理研究  

Structure,stability,and magnetism of (CoAl)n(1≤n≤6) alloy clusters:A first-principlt study

作　　者：郝爱琴 梁瑞瑞[2] 吕瑾 HAO Ai-Qin;LIABG Rui-Rui;LV Jin

机构地区：[1]山西师范大学分析测试中心,临汾041004 [2]山西师范大学化学与材料科学学院,临汾041004

出　　处：《原子与分子物理学报》2020年第5期712-720,共9页Journal of Atomic and Molecular Physics

基　　金：国家自然科学基金青年基金(201301112);教育部博士点基金(20131404120001)。

摘　　要：采用密度泛函理论中的广义梯度近似(DFT-GGA)对(CoAl)n(1≤n≤6)合金团簇的几何、电子结构和磁性进行了系统的研究.计算结果表明(CoAl)n(1≤n≤6)合金团簇在基态附近出现许多能量十分接近的低能量态,有能量简并态存在,表现出经典的过渡金属密堆积结构;同时在(CoAl)5和(CoAl)6团簇中,有磁性双稳态存在.合金团簇的结合能随着团簇尺寸的增大而增大. CoAl团簇获得了最大的带隙,表现出强的化学惰性,带隙在n>3之后出现明显的奇偶变化规律,且整体呈下降趋势,这种现象源于团簇中共价键、离子键的相互竞争.(CoAl)n(1≤n≤6)的总磁矩随尺寸大小呈半梯形状的变化趋势,其中CoAl团簇的磁矩为2μB,(CoAl)2和(CoAl)3磁矩为4μB,(CoAl)4,(CoAl)5和(CoAl)6为6μB,这种磁性变化规律在文中也从磁序排列、电荷转移以及自旋极化等方面进行了详细讨论.The geometries, stabilities, electronic and magnetic properties of the(CoAl)n(1≤n≤6) clusters have been systematically investigated by using density functional theory with generalized gradient approximation(DFT-GGA). The calculation results show that(CoAl)n(1≤n≤6) alloy clusters have many low-energy states with very close energy near the ground state, and exist the energy degenerate states, showing a classic transition metal close-packed structure;meanwhile, the(CoAl)5 and(CoAl)6 clusters exhibit a magnetic bistability state characteristic. The binding energy of alloy clusters increases with the increase of cluster size. CoAl clusters obtained the largest band gap, showing strong chemical inertness. The band gaps show obvious odd-even change after n>3, but the overall trend is decreasing. This phenomenon stems from the covalent and ionic bonds in the clusters competing with each other. The total magnetic moment of(CoAl)n(n≤6) change appears a half-trapezoid shape trend. The magnetic moment of the CoAl cluster is 2μB, the magnetic moment of(CoAl)2 and(CoAl)3 are 4μB, and those of(CoAl)4,(CoAl)5 and(CoAl)6 are 6μB. This change law is explained in detail from the aspects of magnetic sequence arrangement, charge transfer and spin polarization.

关 键 词：(CoAl)n合金团簇 几何结构 稳定性 电子和磁性质 

分 类 号：O641[理学—物理化学]