MODELING THE ELECTRIC-FIELD OF WATER OBTAINED FROM ACCURATE SCF WAVE-FUNCTIONS

Model representations of the electric field calculated with SCF ab initio wavefunctions have been constructed with the distributed multipole approach and effective point charges. Extended basis sets have been used to make benchmark calculations of the dipole, the quadrupole and the octopole moments of a water molecule, and the electric field on several grids around it. Two model representations of the charge density are tested: the distributed multipole-representation and discrete point-charge approach. Comparisons are made with fields obtained from standard basis sets (6-31G, 6-31G*, 6-31G**, 3-21G, 3-21G* and the minimal basis set STO-3G) and point-charge models commonly used in molecular simulations of water (TIP3P, ST2, SPC, TIP4P, Kollman's 5 charges, Dacre's model, MCY and CPC models). © 1990.