An ab initio investigation of the dipole moment of the CO2 ... CO complex

The dipole moment of the CO2...CO van der Waals complex has been studied by highly correlated ab initio methods in the region of the experimental equi librium geometry. Calculations at the CCSD(T) level of approximation combin ed with a basis of at least Pol(ANO) + f quality are needed to provide a re liable value of the dipole moment. The large amplitude motion in the van de r Waals modes reduces the expectation value of the mu(z) by similar to 7%. The enhanced dipole is not primarily due to the field-induced bending of th e CO2 partner, which increases the effective dipole by similar to 20%, but to electronic polarization. (C) 2000 Elsevier Science B.V. All rights reser ved.