A computer-aided quantum chemical study of the N(15)(-) cluster

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Previous studies on odd-numbered anionic nitrogen clusters (N7m, N9m, N11m) indicated open-chain structures as the most stable.
• Investigating larger nitrogen clusters is crucial for understanding their unique structural and energetic properties.

Purpose of the Study:

• To determine the most stable isomer of the N15m cluster.
• To investigate the decomposition pathways and energy barriers of key N15m isomers.
• To compare the stability of N15m isomers with smaller nitrogen clusters.

Main Methods:

• Ab initio (RHF, MP2) and Density Functional Theory (DFT) calculations were employed.
• The 6-31+G* basis set was utilized for initial geometry optimizations.
• Higher level calculations, including B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G*+ZPE, were used for energy refinement.

Main Results:

• The most stable N15m isomer (structure 1) is a complex of cyclic N5m and staggered N10, differing from smaller clusters.
• Decomposition pathways for structure 2 (two aromatic N5 rings linked by N5) and structure 3 (open-chain) were analyzed.
• Energy barriers for N2 and N5m fission in structure 2 were calculated as 18.2 and 14.2 kcal/mol, respectively.
• The N2+N3m fission barrier for structure 3 was found to be 11.2 kcal/mol.

Conclusions:

• The N15m cluster exhibits unique stability characteristics compared to smaller anionic nitrogen clusters.
• Computational analysis provides insights into the stability and reactivity of different N15m isomers.
• The findings contribute to the understanding of nitrogen cluster chemistry and potential applications.