AB-INITIO MP2 STUDY OF THE HF-CENTER-DOT-CENTER-DOT-CENTER-DOT-CLF COMPLEX USING VARIOUS EXTENDED BASIS-SETS AND BOND FUNCTIONS

The stationary points on the intermolecular potential energy surface ( PES) for the HF ... CIF complex have been investigated at the second-o rder Moller-Plesset perturbation theory (MP2) level using various exte nded bais sets, including diffuse functions, and also bond functions. The last ones were placed at different intermolecular positions, for d istinct stationary points. The basis set superposition errors (BSSE) w ere accounted for using the counterpoise method. Besides the anti-H-bo nded and H-bonded minimum energy structures, four transition state str uctures were also located on the PES. It was shown that higher polariz ation functions are required for the description of the anti H-bonded isomer and diffuse functions had to be included for the H-bonded isome r. The bond functions are able to replace the f(Cl, F) and d(H) polari zation functions at a lower computational cost. However, for the H-bon ded isomer intramolecuIar electron correlation also plays an important role. So we have to use diffuse nucleus centered polarization functio ns for an adequate description of intermolecular and intramolecular co rrelation.