3-DIMENSIONAL DISCRETE VARIABLE REPRESENTATION FOR ACCURATE VAN-DER-WAALS VIBRATIONAL-STATES OF COMPLEXES BETWEEN ATOMS AND LARGE MOLECULES, INCLUDING FULLERENES

We discuss the recently developed method for accurate quantum three-di mensional (3D) calculation of excited Van der Waals (VdW) vibrational levels of floppy atom-large-molecule complexes. This method is designe d primarily for highly anisotropic complexes, in which the radius of t he molecule exceeds the equilibrium atom-molecule separation. The 3D d iscrete variable representation (DVR), in Cartesian coordinates, is us ed for all three intermolecular degrees of freedom. The quantum dynami cs of coupled anharmonic VdW vibrations are treated exactly. Our 3D DV R computational methodology is well suited for VdW states delocalized over intermolecular potentials with multiple minima. The scope of its applicability is broad, and includes endohedral complexes of atoms ins ide strongly nonspherical fullerene cages. The method is used to calcu late VdW vibrational levels of 2,3-dimethylnaphthalene Ar (2,3-DMN Ar) up to ca. 60-70 cm(-1) above the ground VdW state. This enabled assig nment of the experimentally observed VdW bands and refinement of the i ntermolecular potential-energy surface for the S-1 state of 2,3-DMN Ar . Using the same 3D DVR code, we also performed the first quantum 3D c alculation of the VdW vibrational states of the endohedral fullerene c omplex Ne@C-70. The regular nodal patterns of the VdW wavefunctions in spected so far suggest weak coupling of the endohedral vibrational mod es of Ne@C-70.