Density functional theory study of [Mg(NH2)2]n(η=1-5) clusters

Possible geometrical structures and relative stabilities of [Mg(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, the electronic structure, vibrational properties, bond properties and ionization potentials are analyzed. The calculated results show the following tendencies: the Mg and N atom are bonded with each other to form catenulate structures. The bond lengths for [Mg(NH2)2]n (n=1-5) clusters are about 0.190-0.234 nm for Mg-N, and 0.101-0.103 nm for the N-H bonds, the bond angles of H-N-H are about 100.2°-107.5°. The population analysis suggests that the natural charge of N atoms are about -1.551e-1.651e, that of Mg atoms are about 1.585e-1.615e, that of H atoms are about 0.369e-0.403e, and that of -NH2 are about -0.784e-0.845e, and the bonds between Mg and -NH2 have strong ionicity. The comparative study of structures and spectra of clusters and crystal show that -NH2 keeps the integrity in the crystal and in clusters.