¹⁷ O Quadrupole Coupling Constants in Water

ABSTRACT An additive framework is developed to describe 17 O 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 17 O 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 17 O NMR observables.