Li9团簇体心立方结构的形成机理和结合能

本文提出了Li9团簇体心立方结构的形成机理，并对此结构的总能量随中心原子到顶点原子间核间距R的变化用芶氏改进的排列通道量子力学方法(MACQM)进行了计算。结果显示曲线在R = 4.77 a0处有一极小值 -67.160922 a.u.，这表明Li9团簇的体心立方结构是可能稳定存在的。在R趋于无穷大时这9个锂原子的总能量为 -66.852240 a.u.，所以形成Li9的总结合能为0.308682 a.u.。因此Li9 团簇的原子平均结合能是0.034298 a.u.或0.933 eV，它大于我们过去计算的Li5团簇正四面体中心结构的原子平均结合能0.632 eV、Li7 团簇正八面体中心结构的原子平均结合能0.674 eV和Li13 团簇正二十面体中心结构的原子平均结合能0.810 eV。故在体心正多面体结构Lin (n= 5 ,7,9,13)中，Li9的体心立方结构有最大的原子平均结合能，这也许是碱金属晶体的晶胞取体心立方结构的一个原因。

Formation Mechanism and Binding Energy for the Body-Centred Cubic Structure of Li9 Cluster

The formation mechanism for the body-centred cubic structure of Li_9 cluster is proposed.The curve of the total energy versus the separation R between the nucleus at the centre and nuclei at the apexes of this structure has quantum mechanics (MACQM).The result shows that the curve has a minimal energy of -67.160922 a.u.at R=4.77a0, which means that the Li_9 cluster may be formed stably in the body-centred cubic structure.When R approaches to infinity, the total energy of nine lithium atoms has the value of-66.852240 a.u., so the binding energy of Li_9 with respect to nine lithium atoms is 0.308682 a.u.Therefore, the binding energy per atom for Li9 is 0.034298 a.u.or 0.933 eV, which is greater than the binding energy per atom of 0.632 eV for the body-centred regular tetrahedral structure of Li_5,0.674 eV for the body-centred regular octahedral structure of Li_7 and 0.810 eV for the body-centred regular icosahedral structure of Li_(13)calculated by us previously. So the body-centred cubic structure of Li_9 has the greatest binding energy for per atom among body-centered regular polyhedral structures of Li_n(n=5,7,9,13), which may be a reason for alkali metal crystal adopting the body-centred cubic structure as its unit cell.