ISOTROPIC AND ANISOTROPIC PROTON CHEMICAL SHIELDING SURFACE OF WATER

Extended-basis-set ab initio calculations have been carried out to obtain the hydrogen chemical shielding tensor for water as a function of the internal geometrical coordinates. The results of the calculations show that the isotropic shielding and the anisotropy are most dependent on the oxygen-hydrogen bond length, and that the variation with the bond length is nearly linear. The anisotropy shows a significantly greater dependence on stretching the OH bond of the other hydrogen than does the isotropic shielding. Furthermore, we find that the deformation of water's structure that occurs in ice Ih is associated with a decrease in anisotropy instead of the expected increase.