Zero-Point Vibrational Corrections to One-Electron Properties of the Water Molecule in the Near-Hartree—Fock Limit

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Abstract
The zero‐point vibrational motion of the water molecule in its ground electronic state is analyzed with a near‐Hartree—Fock potential energy surface constructed from a (9s5p2d/4s1p) /[4s3p2d/2s1p] basis set of contracted Gaussian orbitals. The harmonic and cubic force constants relative to the computed minimum are obtained, and a normal coordinate analysis is carried out for several isotopic variants. A set of one‐electron properties including molecular moments, field gradients, forces, and densities is computed at each point on the potential surface, and then averaged over the zero‐point motion with a vibrational wavefunction which contains anharmonicity terms through the cubic constants. The vibrational corrections are typically about 1% of the equilibrium values, but are as large as 20% in cases such as the 17O quadrupole coupling constant along the C2 axis. The theoretical isotope shifts for the quadrupole moments of H2O and D2O are in good agreement with experiment. Predictions are made for isotope shifts in other properties. A b initio values of the bond and angle displacement coordinates and their root‐meansquare amplitudes are also determined.