VIRIAL-THEOREM DECOMPOSITION AS A TOOL FOR COMPARING AND IMPROVING POTENTIAL-ENERGY SURFACES - GROUND-STATE LI(3)

The virial theorem has been used to decompose existing potential-energ y surfaces for the ground state of Li3 into the electronic, kinetic an d potential components, and to improve some of the physical attributes to the most aocurate potential-energy surface for this system. The be haviour of these components and the total energy for a C2v uniform-sca ling cut of the various surfaces is compared. The individual contribut ions of both two- and three-body energy terms are also discussed. Spec ific results are presented for the Varandas-Morals and Thompson et al. potential-energy functions, in addition to the recent double many-bod y expansion (DMBE) potential-energy surface, this being the only exist ing Li3 surface for which the normalization of the kinetic field, appl ied by the virial theorem, is satisfied. By slightly modifying adjusta ble parameters of the latter surface, an improved DMBE surface has bee n obtained with qualitatively correct trends in the kinetic and potent ial energy profiles. The implications for the ideal general form of a potential-energy surface are also assessed.