Ab initio characterization of the structure and energetics of the ArHF complex

The ArHF complex has been investigated using correlation consistent basis sets at several levels of theory, including Moller-Plesset perturbation theory (MP2, MP3, MP4) and coupled cluster techniques [CCSD, CCSD(T)]. The three stationary points (the primary linear Ar-HF minimum, the secondary linear Ar-FH minimum, and the interposed transition state TS) on the counterpoise-corrected potential energy surface have been characterized. Calculations with the aug-cc-pV5Z basis set predict D-e for the Ar-HF minimum to be (with estimated complete basis set limits in parentheses) -215 (-218) cm(-1) for MP3 and -206 (-211) cm(-1) for CCSD(T). For the Ar-FH minimum and the TS, calculations with the d-aug-cc-pVQZ sets predict D-e's (and CBS limits) of -97 (-99) and -76 (-78) cm(-1) (MP4) and -93 (-94) and -75 (-76) cm(-1) [CCSD(T)], respectively. The corresponding values for the H6(4,3,2) potential of Hutson [J. Chem. Phys. 96, 6752 (1992)] are -211.1 +/- 4 cm(-1), -108.8 +/- 10 cm(-1), and -82.6 +/- 10 cm(-1). While the agreement of our CCSD(T) estimate with Hutson's value is excellent for the global minimum, it is less so for the other two stationary points, suggesting that the H6(4,3,2) potential may be too attractive around the secondary minimum and the transition state. (C) 1997 American Institute of Physics.