Mg_3N_2团簇吸附H的密度泛函理论研究

运用密度泛函理论(DFT)中的杂化密度泛函B3LYP方法在6-311G*基组水平上对Mg_3N_2H_m(m=1~4)和(Mg_3N_2)_nH_m(n=2~4,m=1~2)团簇的可能几何结构进行优化,预测了其最稳定结构,并对最稳定结构的电子结构,成键特性,电荷分布,振动特性及稳定性等进行分析。结果表明:当团簇吸附H原子少于N原子数目时,一般形成-NH基;随着团簇吸附H原子数目的增加,当所有N原子吸H形成-NH基后,才有-NH基吸附H原子形成-NH_2基;但并不是所有-NH基全部形成-NH_2基的饱和结构,此时部分H原子会吸附于Mg原子上形成MgH结构。H原子易吸附于凸出的、包含孤对电子的N原子上;由于孤对电子间的排斥作用,H原子的吸附位置呈相互远离趋势。团簇中N-H之间是共价键作用,而Mg-H间是离子键作用,-NH和-NH_2基在团簇中保持完整性,团簇可以很好地描述晶体的储氢行为。

Density Functional Theory Study On Mg3N2 clusters adsorbed H

Possible geometrical structure, relative stabilities of Mg3N2Hm(m=1-4) and (Mg3N2)nHm(n=2-4,m=1-2) clusters are studied by using the density functional theory (B3LYP) with 6-311G* basis sets. For the most stable isomers of Mg3N2Hm(m=1-4) and (Mg3N2)nHm (n=2-4,m=1-2) clusters, the electronic structure,bonding characteristics, charge distribution, vibrational properties and relative stabilities are analyzed. When the number of the adsorbed H atoms less than that of N atoms, it mainly forms -NH group. And then some H atoms are adsorbed by the -NH groups and it forms -NH2 groups while some other H atoms are adsorbed by Mg forming MgH when all the N atoms bond as -NH. H atom is easialy adsorped on N atom which is projecting and contains the lone pair electrons. Due to the repulsion between the lone pair electrons, the adsorption positions of H atoms were away from each other. The N-H in cluster showed covalent interaction, where the Mg-H showed ionic bond interaction. The properties of-NH and -NH2 group are consistent with that of crystals, so the cluster can describe the behavior of the hydrogen storage in crystals.