Ab initio calculations predict that structures P(N-n)(m) (n = 3, 4; in = 1-4; with linear N-3, tetrahedral N-4, and square N4) correspond to local energy minima characterized by having real frequencies for all eigenvectors of the Hessian matrix. The central P atom often prefers having an odd number of bonds, although we also found some stable structures where P is evenly bonded. The special role of the phosphorus atom in the a geometrical arrangements of the P(N-n)(m) systems was investigated. The low barriers of P(N-4)(m) in the gas phase decomposition reactions mean that these nitrogen-rich systems require external stabilization if they are to be used as high-energy density materials or starting materials for further syntheses.