基于密度泛函理论的镧镍团簇结构和性质研究

【作者】 刘娜；

【导师】 刘英；

【作者基本信息】 河北师范大学 ， 凝聚态物理， 2006， 硕士

【摘要】 原子或分子团簇作为一种新的物质形态,它的性质具有明显的尺寸依赖性,团簇结构与性质的研究对于理解物质从微观到宏观的过渡具有重要作用。团簇由于其特殊的物理化学性质,已引起物理、化学和材料等领域的广泛的关注。特别是混合/掺杂团簇,由于其组成、结构及性质的多样性,在电子、工程、催化等领域具有广泛的应用前景。 团簇的电子结构与几何结构密切相关,它们相互影响和调节以使团簇的自由能取得极小值。原子团簇的几何结构决定了其化学键结构和电子结构的性质,因此确定基态结构就是团簇研究的首要任务。稀土元素镧由于其结构的特殊性以及镧镍材料在储氢方面的应用而受到人们的广泛关注。本文基于密度泛函理论的第一原理计算—DMol方法,采用最流行的BLYP交换关联函数(Becke交换梯度修正函数和Lee-Yang-Parr关联梯度函数结合)和缀加极化函数的双数值原子基组DNP,对镧镍(总原子数为7)混合小团簇的稳定构型、电子结构和磁特性进行了研究。得到了各种情况下的稳定结构,发现镧镍混合团簇多数情况下都有一定的磁性,对称性在决定团簇磁性大小方面起决定作用,并且在镧镍混合团簇中,存在着电荷从镧原子向镍原子的转移。为进一步对中等尺度甚至于大尺度团簇的结构及性质计算奠定了基础。更多还原

【Abstract】 Clusters, as a new form of substance, show many novel and unique properties both in physics and chemistry. The detailed knowledge of the atomic structure of clusters, and the dependence of structure on size is an intriguing issue. Due to their unique geometrical arrangements, physical, chemical, electronic and magnetic properties, the studies of clusters can greatly facilitate and promote the fundamental and applied research of many related subjects, such as physics, chemistry and materials.The electronic structure and chemical bond of cluster dominate geometric configuration, contrariwise, geometric configuration reflects the feather of chemical band and electronic structure. Therefore, unambiguous assignment of the ground state geometric configuration is a principal task. Because of the special construction of Lanthanum and the application of Lanthanum-Nickel materials, we employed first principles calculation-- DMol method that based on the density-functional theory, and we used the BLYP exchange-correlation functional and a double-numerical basis with polarized functions (DNP). Structural and electronic properties of Lanthanum-Nickel mixed clusters (total atom number is less than seven) have been systematically studied. We choose transition mental—Nickel as theimpurity, we got various stable structures in all conditions, meanwhile we found that Lanthanum-Nickel mixed clusters usually have certain magnetism. Besides the magnitude of magnetism was determinated by symmetrical characteristic, and usually some electron charges moved from Lanthanum to Nickel. It established the foundation for the calculation of the structural and electronic properties of the middle scale clusters, even those of the large-scale clusters.更多还原