Ab initio based double-sheeted DMBE potential energy surface for N3(2A″) and exploratory dynamics calculations.

We report a global accurate double-sheeted potential energy surface for the lowest doublet states with (2)A″ symmetry of the N(3) radical using the double many-body expansion method. The functional form ensures by construction the degeneracy of the two adiabatic sheets along the D(3h) line and the corresponding cusp behavior. Calibrated from multireference configuration interaction energies, it reproduces all the predicted stationary structures on both sheets and ensures a correct description of the dissociation limits. A test quasiclassical trajectory study of N((2)D) + N(2) collisions is also reported in the lowest adiabatic sheet of the potential energy surface. The results commend it for both classical and quantum dynamics studies, while serving as a building block for the potential energy surfaces of larger nitrogen allotropes and azides.