THEORETICAL STUDY OF THE STRUCTURES AND PROPERTIES OF (Cl2AlN3)n (n=2-4) CLUSTERS

Density functional theory has been employed to study the molecular geometries, energies, infrared vibrational spectra, and thermodynamic properties of the clusters (Cl2AlN3)(n) (n = 1-4)) at the B3LYP/6-311+G* level. The optimized clusters (Cl2AlN3)(n) (n = 2-4) all possess cyclic structures formed by Al atoms bridged by the alpha-nitrogen of the azide groups, and azido in azides has linear structure. The relationships between geometrical parameters and oligomerization degree n are discussed. The gas-phase structures of the trimers prefer to exist in boat-twisting conformation. As for the tetramer, the S-4 symmetry structure is the most stable. The infrared spectra are obtained and assigned by vibrational analysis. Trends in thermodynamic properties with temperature and oligomerization degree n are discussed, respectively. A study of their thermodynamic properties suggests that monomer 1A forms clusters (2A, 3A and 3B) can occur spontaneously in the gas phase at temperatures up to 800 K. However, monomer 1A forms tetramers can occur spontaneously at temperatures below 600 K.