Thermodynamics of NO+center dot N-2: Atmospheric relevance

The NO+. N-2 cationic complex is studied using high-level ab initio calcula tions. The geometry is found to be a skewed T shape, with two linear statio nary points corresponding to the N-O+. N-N and N-N . N-O+ configurations. A t the highest level of theory, CCSD(T)/aug-cc-pVQZ//CCSD(T)/aug-cc-pVTZ, th e interaction energy is estimated to be 1950 cm(-1) (5.6 kcal mol(-1)), fro m which a Delta H-298 interaction enthalpy value of 4.9 kcal mol(-1) was de rived. By using the well-established heat of formation of NO+, it was possi ble to derive a standard Delta H-f(298) value of 230.4 kcal mol(-1) for NO. N-2. In addition, the enthalpy, entropy, free energy and equilibrium cons tants were calculated for the dissociation of the complex, as a function of altitude, for the earth's atmosphere.