¹⁷O Quadrupole Coupling Constants in Water

An additive framework is developed to describe ¹⁷O quadrupole coupling constants (QCC's) in hydrogen-bonded water systems across isolated molecules, finite clusters, and ice-like environments. Density functional theory calculations using optimized geometries show that ¹⁷O QCC variations are primarily governed by hydrogen-bond interactions. A dimer model identifies hydrogen-bond distance as the dominant geometric factor, while angular and intramolecular distortions are minor. In ice and water clusters, first-nearest-neighbor interactions provide the largest contribution and are well captured by an additive donor-acceptor scheme, with improved accuracy upon inclusion of hydrogen bond distance dependence. Second nearest neighbor effects introduce smaller but systematic negative corrections arising from hydrogen-bond network asymmetry, restoring near-quantitative agreement with full calculations. The resulting model provides a computationally efficient and physically interpretable approach for predicting electric field gradients in aqueous environments and linking molecular simulations with ¹⁷O NMR observables.