A computational investigation of the electronic properties of Octahedral Al (n) N (n) and Al (n) P (n) cages (n=12, 16, 28, 36, and 48)

作者：Saeedi Marzieh; Anafcheh Maryam; Ghafouri Reza; Hadipour Nasser L^*

来源：Structural Chemistry, 2013, 24(2): 681-689.

DOI：10.1007/s11224-012-0119-7

• AlN cages
• AlP cages
• DFT
• NMR
• CS parameters
• NBO
• Hydrogen storage

Density functionla theory (DFT) calculations are performed to characterize geometric and electronic features of the octahedral Al (n) N (n) and Al (n) P (n) cages (n = 12, 16, 28, 32, and 48). Toward this aim, N-15, Al-27, and P-31 chemical shielding (CS) tensors as well as natural charge analyses are calculated for the optimized structures. CS parameters detect three distinct electronic environments for atoms within the Al (n) N (n) and Al (n) P (n) cages. The chemical shifts of N2 sites belonging to a hexagon and surrounded by three hexagons and a square obtained are different from those of N3 sites belonging to a hexagon that is surrounded only by hexagons-due to different curvatures exerted at the sites with different local structures. In addition, there is an increasing tendency in the Delta sigma values of the three local structures, Delta sigma (N1) > Delta sigma (N2) > Delta sigma (N3), N1 sites belonging to four-membered rings. The chemical shieldings of those Al and P sites belonging to a hexagon that is surrounded only by hexagons in the cages (360.7-366.7 and 496.5-514.7 ppm) are close to those previously reported for AlP nanotubes. Three distinct electrostatic environments around the N, Al, and P nuclei are also confirmed by the calculated natural charges. It should be noted that the positively charged Al atoms on the cages turn out to be the available sites for adsorption of H2 molecules.

• 出版日期2013-4