Nuclear spin optical rotation (NSOR) of linearly polarized light, due to the nuclear spins through the Faraday effect, provides a novel probe of molecular structure and could pave the way to optical detection of nuclear magnetization. We determine computationally the effects of the liquid medium on NSOR and the Verdet constant of Faraday rotation (arising from an external magnetic field) in water, using the recently developed theory applied on a first-principles molecular dynamics trajectory. The gas-to-liquid shifts of the relevant antisymmetric polarizability and, hence, NSOR magnitude are found to be -14% and -29% for (1)H and (17)O nuclei, respectively. On the other hand, medium effects both enhance the local electric field in water and, via bulk magnetization, the local magnetic field. Together these two effects partially cancel the solvation influence on the single-molecular property. We find a good agreement for the hydrogen NSOR with a recent pioneering experiment on H(2)O(l).

Nuclear magnetic resonance (NMR) shielding tensors for the oxygen and hydrogen nuclei, as well as nuclear quadrupole coupling tensors for the oxygen and deuterium nuclei of water in the liquid and gaseous state, are calculated using Hartree-Fock and density functional theory methods, for snapshots sampled from Car-Parrinello molecular dynamics trajectories. Clusters representing local liquid structures and instantaneous configurations of a single molecule representing low-density gas are fed into a quantum chemical program for the calculation of the NMR tensors. The average isotropic and anisotropic tensorial properties of 400 samples in both states, averaged using a common Eckart coordinate frame, are calculated from the data. We report results for the gas-to-liquid chemical shifts of (17)O and (1)H nuclei, as well as the corresponding change in the nuclear quadrupole couplings of (17)O and (2)H. Full thermally averaged shielding and quadrupole coupling tensors are reported for the gaseous and liquid-state water, for the first time in the case of liquid. Electron correlation effects, the difference of classical vs quantum mechanical rovibrational averaging, and different methods of averaging anisotropic properties are discussed.

Nuclear magnetic resonance (NMR) parameters are determined theoretically for the oxygen and hydrogen/deuterium nuclei of differently hydrogen-bonded water molecules in liquid water at 300 K. The parameters are the chemical shift, the shielding anisotropy, the asymmetry parameter of shielding, the nuclear quadrupole coupling constant, and the asymmetry parameter of the nuclear quadrupole coupling. We sample instantaneous configurations from a Car-Parrinello molecular dynamics simulation and feed nuclear coordinates into a quantum chemical program for the calculation of NMR parameters using density-functional theory with the three-parameter hybrid exchange-correlation (B3LYP) functional. In the subsequent analysis, molecules are divided into groups according to the number of hydrogen bonds they possess, and the full average NMR tensors are calculated separately for each group. The classification of the hydrogen-bonding cases is performed using a simple distance-based criterion. The analysis reveals in detail how the NMR tensors evolve as the environment changes gradually from gas to liquid upon increasing the number of hydrogen bonds to the molecule of interest. Liquid-state distributions of the instantaneous values of the NMR properties show a wide range of values for each hydrogen-bonding species with significant overlap between the different cases. Our study shows how local changes in the environment, along with classical thermal averaging, affect the NMR parameters in liquid water. For example, a broken or alternatively extra hydrogen bond induces major changes in the NMR tensors, and the effect is more pronounced for hydrogen or deuterium than for oxygen. The data sheds light on the usefulness of NMR experiments in investigating the local coordination of liquid water.