AbstractThe potential energy surface of the van der Waals system HeLi2 is computed for the case in which the system hasC2vsymmetry and at the Li‐Li distance (5.005 bohrs). A comparative study of the results for the two methods used,ab initioHartree‐Fock and second‐order Møller‐Plesset, and several basis sets, ranging from minimal to near Hartree‐Fock quality, is also done. The results show the importance of correcting the basis set superposition error, and the need, in order to obtain a good description of the potential, of basis sets with polarization functions on all the atoms, when the Møller‐Plesset method is used. At the Hartree‐Fock level, the MINI‐1 basis gives results almost of the same quality as the near H