ACCURATE CALCULATION OF THE BINDING-ENERGY OF THE WATER DIMER

The binding energy of the water dimer is calculated at the MP2 level u sing efficient basis sets augmented with bond functions. The intermole cular energy is determined by the supermolecular approach and the basi s set superposition error is corrected by the counterpoise method. Bon d functions are found useful and very effective in recovering the disp ersion energy, which is traditionally achieved by polarization functio ns. The calculated binding energy of the water dimer is systematically converged to a value of 4.75 kcal mol-1 as bond functions are gradual ly added to nucleus-centered basis sets.