``Floating'' Hydrogen Densities in Some Molecules of the Type XHn

The model of ``floating'' hydrogen densities was suggested initially by McDonald in an analysis of the electron density for NH4+. The model, as used here, is an attempt to represent the molecular radial distribution as a superposition of the radial densities obtained from the ``best'' electronic wave functions (in the sense of the variation method) for the constituent atoms, the centers of the unperturbed hydrogen distributions being allowed to ``float'' inward along the bonds. The model was applied to H2O and CH4 and the molecular and bond dipole moments were calculated. Thus for H2O, which alone possesses a resultant moment, some insight could be obtained into the accuracy of the angular dependence of the density pref dicted by such a model. Comments were also made on NH4+ and NH3. Further, the application of an approximate formula of Carter enabled a determination to be made of the paramagnetic contribution to the molar diamagnetic susceptibility.