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化学学报
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化学学报 ›› 2008, Vol. 66 ›› Issue (18): 2030-2036. 上一篇    下一篇

研究论文

[Ca(NH2)2]n (n＝1～5)团簇的密度泛函理论研究

陈玉红*,a,b 康 龙b 张材荣a 罗永春b 李延龙a 元丽华a

  

  1. (a兰州理工大学物理系 兰州 730050)
    (b兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室 兰州 730050)

  • 投稿日期:2008-02-01 修回日期:2008-04-04 发布日期:2008-09-28
  • 通讯作者: 陈玉红

Density Functional Theory Study on [Ca(NH2)2]n (n＝1～5) Clusters

CHEN, Yu-Hong *,a,b KANG, Long b ZHANG, Cai-Rong a LUO, Yong-Chun b
LI, Yan-Long a YUAN, Li-Hua a
  

  1. (a Department of Physics, Lanzhou University of Technology, Lanzhou 730050)
    (b State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology,
    Lanzhou 730050)
  • Received:2008-02-01 Revised:2008-04-04 Published:2008-09-28
  • Contact: CHEN, Yu-Hong

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用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对[Ca(NH2)2]n (n＝1～5)团簇各种可能的构型进行几何结构优化, 预测了各团簇的最稳定结构. 并对最稳定结构的振动特性、成键特性、电荷特性等进行了理论研究. 结果表明: 团簇易形成环状结构, 以金属Ca原子团簇作为骨架, NH2基结合在金属团簇骨架上, 并主要是Ca—N成键和Ca—Ca成键. 团簇中Ca—N键长为0.225～0.257 nm, Ca—Ca键长为0.312～0.354 nm, N—H键长为0.102～0.103 nm, H—N—H键角为102.9°～104.2°; 团簇中Ca原子的自然电荷在1.657e～1.720e之间, N原子的自然电荷在－1.543e～－1.592e之间, H原子的自然电荷在0.349e～0.367e之间, Ca原子和NH2基之间相互作用呈现较强的离子性；对比团簇和晶体的结构及IR谱表明, NH2基在团簇和晶体中的结构基本一致.

关键词: [Ca(NH2)2]n (n＝1～5)团簇, 密度泛函理论, 结构与性质, 储氢材料

Possible geometrical structures and relative stabilities of [Ca(NH2)2]n (n＝1～5) clusters are studied by using the hybrid density functional theory (B3LYP) with 6-31G* basis sets. For the most stable isomers, electronic structures, vibrational properties, bonds properties, and ionization potentials are analyzed. The calculated results show that N—Ca and Ca—Ca bonds are favorable in the clusters, in which NH2 is bound to the framework of Ca atomic clusters forming ring-like structures. The bond lengths in [Ca(NH2)2]n (n＝1～5) clusters are 0.225～0.257 nm for Ca—N, 0.312～0.354 nm for Ca—Ca, and 0.102～0.103 nm for N—H bonds, respectively. The bond angles of H—N—H are 102.9°～104.2°. The population analysis suggests that the bonds between Ca and NH2 are of strong ionicity. The natural charges are －1.543e～－1.592e for N atoms, 1.657e～1.720e for Ca atoms, and 0.349e～0.367e for H atom, respectively. The comparative study of structures and spectrum between clusters and crystal shows that the structure of NH2 in clusters is consistent with that in crystal.

Key words: [Ca(NH2)2]n (n＝1～5) clusters, density functional theory, structure and property, hydrogen storage material