Accurate Study of the Two Lowest Singlet States of HN3: Stationary Structures and Energetics at the MRCI Complete Basis Set Limit

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-05, Vol.117 (19), p.4044-4050
• Main Authors: Galvão, B. R. L, Varandas, A. J. C
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Bond strengths, dissociation energies; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Molecular properties and interactions with photons; Physics; Properties of molecules and molecular ions
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp402090s

The two lowest singlet potential energy surfaces of the hydrazoic acid are explored using high-level quantum chemistry calculations, revealing isomeric forms, transition states, and a new path for the nitrogen ring-closing mechanism in the ground state. The reaction of cyc-N3 with hydrogen is shown to proceed through a barrierless path that dissociates to N2 + NH(1Δ) without reaching the HN3 global minimum. Several intersections between the two states are localized for both N3 isomers near the N3 + H dissociation. The energies of stationary structures and dissociation asymptotes are obtained with the multireference configuration interaction method at the complete basis set limit. A comparison with recent experimental data regarding the H–N3 bond strength and the dissociation barrier in the excited state shows that the present results are of chemical accuracy (∼1 kcal mol–1).