Multireference configuration interaction methods are used to calculate potential curves, dissociation energies, and vibration-rotation energy levels for HCl and N2. These calculations use basis sets optimized in a previous study. The potential curves show very good agreement with experimental (RKR) data. Both CI and RKR data are accurately fitted by five-parameter generalized Morse functions. Spectroscopic parameters calculated for HCl are De = 4.62 eV, Re = 1.277 Å, ωe = 3023 cm-1, ωexe = 52.9 cm-1 Be = 10.67 cm-1, and αe = 0.338 cm -1 (experimental v, J values give 4.62 eV, 1.275 Å, 2989 cm-1, 51.2 cm-1, 10.71 cm-1, and 0.341 cm -1, respectively) and for N2 are De = 9.96 eV, Re = 1.106 Å, ωe = 2344 cm-1, ωexe = 13.9 cm-1, Be = 1.934 cm-1, αe = 0.014 cm-1 (experimental v, J values give 9.91 eV, 1.098 Å, 2363 cm-1, 14.7 cm-1, 1.960 cm-1, and 0.015 cm-1, respectively). This good agreement with experiment is obtained using small but carefully balanced basis sets containing bond functions, an approach which we suggest should be adopted in calculations involving molecular dissociation.

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Journal The Journal of Chemical Physics
Wright, J.S, & Buenker, R.J. (Robert J.). (1985). MRD-Cl potential surfaces using balanced basis sets. III. HCl and N 2. The Journal of Chemical Physics, 83(8), 4059–4068.