TOWARDS QUANTITATIVE DIATOMICS-IN-MOLECULES MODEL FOR THE WATER MOLECULE

The diatomics-in-molecules (DIM) model is developed for the water mole cule which allows us to extend the set of molecular parameters quantit atively predicted with the help of this theory. It is shown that not o nly mixing of the neutral and ionic states when constructing the polya tomic basis functions as prescribed by the previous works is necessary for an accurate description of the ground state potential energy surf ace, but certain corrections due to a multicenter charge distribution in the polyatomic molecule are required. The results of new ab initio calculations for the potential curves of the ion-pair states of OH are employed. Finally, the energies of H2O are obtained from the 9 X 9 DI M Hamiltonian matrix what makes feasible further applications of this surface in molecular dynamics simulations of water containing intermol ecular complexes. The molecular constants predicted by DIM including h armonic frequencies are perfectly consistent with the reference data. The H2O potential energy surface of spectroscopic accuracy created by Partridge and Schwenke have been used for the point-by-point compariso n of DIM and ab initio results showing the efficiency of the present m odel. (C) 1998 Elsevier Science B.V. All rights reserved.