The nature of the hydrated excess proton in water

Article Abstract:

Ab initio path integral simulations, including time-independent equilibrium thermal and quantum fluctuations of nuclei, were used to determine interatomic interactions from an electronic structure. The hydrated proton was found to form a fluxional defect in the hydrogen-bonded network. This becomes delocalized over several hydrogen bonds due to quantum fluctuations. The proton is thus considered part of a low-barrier hydrogen bond where tunnelling is slight and the transition-state theory does not apply.

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Anisotropy of earth's D" layer and stacking faults in the MgSiO(sub 3) post-perovskite phase

Article Abstract:

A novel simulation technique, first-principles metadynamics is used to identify a family of low-energy polytypic stacking-fault structures intermediate between the perovskite and post-perovskite phases of MgSiO(sub 3) which is considered as a Earth's lowermost mantle, that is D" layer. Metadynamics trajectories identify plane sliding involving the formation of stacking faults as the most favorable pathway for the phase transition, and as a likely mechanism for plastic deformation of both the phases.

United States, Analysis, Environmental aspects, Anisotropy, Deformations (Mechanics), Deformation, Perovskite

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Tunnelling and zero-point motion in high-pressure ice

Article Abstract:

Research shows that ice contains asymmetric hydrogen bonds with proton-ordered arrangements at low pressure. Increasing pressure results in a proton-disordered asymmetric phase due to translational proton tunnelling. Hydrogen-bond symmetrization and delocalized protons are caused by zero-point fluctuations at higher pressures. The protons become more localized when a single-well potential exists.

Ice, Nuclear polarization

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