Knowledge Bank

A three-dimensional, analytic potential energy surface for CO$2$-He that explicitly incorporates its dependence on the $Q3$ asymmetric-stretch normal-mode coordinate of the CO$2$ monomer, has been obtained by least-squares fitting new {\em ab initio} interaction energies to a new potential form. The potential energy values were obtained from a supermolecule calculation performed at the CCSD(T) level using an aug-cc-pVQZ basis set supplemented with bond functions, and the full counterpoise correction was applied. These points were fitted to a 3-dimensional generalization of the ``Morse/Long-Range'' potential function form}\ (2007, in press).} which incorporates theoretically known angle-dependent long-range inverse-power dispersion coefficients. The three-dimensional discrete-variable representation method was employed to calculate the rovibrational eigenvalues, without separating the inter- and intramolecular nuclear motions, and our simulated infrared spectra in $\nu 3$ region of CO$2$ is compared with experiment.}\ {\bf 101}, 8351 (1994).} This three-dimensional surface will be used to predict the IR vibrational frequency shifts which have been observed for CO$2$-(He) clusters with $N$ up to 20.}\ {\bf 121}, 181 (2004). }