Ab initio investigation of the N2 endash HF complex: Accurate structure and energetics

Augmented correlation consistent basis sets of double (aug-cc-pVDZ), triple (aug-cc-pVTZ), and modified quadruple zeta (aug-cc-pVQZ') quality have been employed to describe the N2 endash HF potential energy surface at the Hartree endash Fock level and with single reference correlated wave functions including Mo/ller endash Plesset perturbation theory (MP2, MP3, MP4) and coupled cluster methods [CCSD, CCSD(T)]. The most accurate computed equilibrium binding energies De are (with counterpoise correction) 810 cm-1 (MP4/aug-cc-pVQZ') and 788 cm-1 [CCSD(T)/aug-cc-pVQZ']. Estimated complete basis set limits of 814 cm-1 (MP4) and 793 cm-1 [CCSD(T)] indicate that the large basis set results are essentially converged. Harmonic frequencies and zero-point energies were determined through the aug-cc-pVTZ level. Combining the zero point energies computed at the aug-cc-pVTZ level with the equilibrium binding energies computed at the aug-cc-pVQZ' level, we predict D0 values of 322 and 296 cm-1, respectively, at the MP4 and CCSD(T) levels of theory. Using experimental anharmonic frequencies, on the other hand, the CCSD(T) value of D0 is increased to 415 cm-1, in good agreement with the experimental value recently reported by Miller and co-workers, 398±2 cm-1. copyright 1996 American Institute of Physics