(Mg(BH4)2)n团簇结构与性质的密度泛函理论研究
Study on the Structure and Properties of Mg(BH4) 2) n Clusters by Density Functional Theory

采用了密度泛函理论中的杂化密度泛函B3LYP方法，在6-31G*基组水平上对[Mg(BH4)2]n(n=1-3)团簇的结构进行了优化，几何结构优化时自旋多重度取了1、3、5等多种情况进行计算。最后对最稳定结构的振动特性、成键特性、电荷特性和稳定性等进行了研究。结论表明：团簇最稳定结构易形成链状结构，其中Mg-B键长为0.210～0.253nm，-BH4基中靠近Mg原子处的B-H键长约为0.125nm、远离Mg原子处的B-H键长为0.119nm。对比团簇和晶体的光谱结构表明，-BH4基在团簇和晶体中结构基本一致。Mg原子的自然电荷在1.687~1.757e之间，B原子的自然电荷在-0.702~-0.788e之间，H原子基本不参与电荷转移，其自然电荷在-0.094~0.070e之间。团簇中Mg原子和-BH4基之间相互作用呈现较强的离子性，Mg(BH4)2团簇具有相对较高的动力学稳定性。
The structure of [Mg(BH4)2]n(n=1-3) clusters are optimized at 6-31G* basis set using the hybrid density functional B3LYP method in density functional theory. Geometric structure optimization of the spin multi-degree taken 1、3、5 and other conditions to calculate. For the most stable isomers, electronic structures, vibrational properties, bonds properties, and ionization potentials are analyzed. The results show that the most stable structure of the cluster is easy to form a chain structure, in which the Mg-B bond length is 0.210 ~ 0.253nm, the B-H bond length near the Mg atom in the -BH4 group is about 0.125nm, and the B-H bond away from the Mg atom long to 0.119nm. The comparative study of spectrum between clusters and crystal shows that the structure of -BH4 in clusters is consistent with that in crystal. The natural charges are 1.687~1.757e for Mg atoms, -0.702~-0.788e for B atoms, and -0.094~0.070e for H atom, respectively. The interaction between Mg atoms and -BH4 groups in the clusters showed strong ionic properties and Mg (BH4)2 clusters have relatively high kinetic stability.