Density functional theory study on the structure and properties of (HMgN 3 ) n ( n =1–5) clusters

We optimize the possible geometrical cluster structures and predicte relative stability of (HMgN 3 ) n ( n =1–5) by using the hybrid density functional theory (B3LYP) with 6-311G * basis sets. And the most stable isomers of (HMgN 3 ) n ( n =1–5) clusters, the bond properties, charge distributions, vibrational properties, and stability are analyzed theoretically. The calculated results show that the most stable HMgN 3 has a linear structure, the (HMgN) n ( n =2,5) clusters have the most stable structures in which an N atom in a sub-system and metal atom in another sub-system constitute an Mg–N–Mg structure. And the most stable structures of (HMgN 3 ) n ( n =3,4) clusters are the chain structures in which the nitrogen cardinal extremity position N atom and the Mg atom form a ring structure; the metal Mg atoms in the most stable structure show charge positivity, and H atom show charge negativity. The middle N atoms of azido show charge positivity, the N atoms on both sides of azido show charge negativity; what's more, the N atoms influenced by Mg atoms directly show a more charge negativity. Mg–N bond and Mg–H bond are the typical ionic bond; the bond between N atoms in azido is the covalent bond. The infrared spectra of the most optimized (HMgN 3 ) n ( n =1–5) clusters have three vibrational sections, the strongest vibrational peak lies in 2258–2347 cm -1 , and the vibrational mode is anti-symmetric stretching vibration of N–N bonds in azido. Analysis of stability shows that (HMgN 3 ) 3 clusters are more stable than other clusters.