ELECTRON-AFFINITIES AND THERMODYNAMIC PROPERTIES OF SOME TRIATOMIC SPECIES

The electron affinities of HCO2. and the XYZ triatomic species: N3., OCN., SCN., NO2., O3, SO2, ClO2., CO2, and N2O were calculated by ab initio methods at the G2 level of theory. Comparison of the calculated values for N3., NO2., O3, and SO2 with accurate measurements indicates that the G2 procedure is capable of reproducing thc experimental results with an average error of 0.06 eV. The present ab initio calculations of structures and electron affinities are compared with earlier ones. Calculations for the other species, where the experimental results are less extensive or less accurate, provide evidence for preferred values. Thermodynamic properties, C(p)0, S0, H-0 - H-0(0), DELTA-H(f)0(T), and DELTA-G(f)0(T) for the above species and the corresponding negative ions were calculated as functions of temperature by means of standard statistical thermodynamic methods and using the most accurate molecular properties available from experiment or the G2 results.