Theoretical probe on the structure and properties of CnN2n (n=2-5) clusters

Four new CnN2n (n=2-5) clusters are predicted to be stable by geometry optimization and vibration frequency verifications at B3PW91/6-31G* density functional (DFT) level. These clusters are in high symmetry (Dnh) and are energetic species. Three low-lying vertical electronic excitation energies are predicted by the time dependent (TD) B3PW91/6-31G* calculations. By employing accurate model chemistry method at G3MP2 level, the following thermo-chemical properties are predicted quantitatively at 298.15 K and standard pressure. Enthalpies of formation are 916.1, 1275.7, 1455.5, and 1679.1 kJ/mol for n=2-5, respectively. Adiabatic ionization potentials for C2N4, C3N6 and C4N8 are 954.7, 973.2 and 924.8 kJ/mol. Vertical ionization potentials are 982.3, 1017.7, 961.6 and 981.4 kJ/mol. Electron affinities are 82.2, 88.3, 113.0 and 145.0 kJ/mol. Combustion enthalpies are −1726.2, −2491.0, −3075.8 and −3704.6 kJ/mol for n=2-5, respectively. Four categories of bond breaking types and energies are discussed.