HydrogenBond Asymmetric Local Potentials in CompressedIce.

A combination of the Lagrangian mechanicsof oscillators vibration,molecular dynamics decomposition of volume evolution, and Raman spectroscopyof phonon relaxation has enabled us to resolve the asymmetric, local,and short-range potentials pertaining to the hydrogen bond (O:H–O)in compressed ice. Results show that both oxygen atoms in the O:H–Obond shift initially outwardly with respect to the coordination origin(H), lengthening the O–O distance by 0.0136 nm from 0.2597to 0.2733 nm by Coulomb repulsion between electron pairs on adjacentoxygen atoms. Both oxygen atoms then move toward right along the O:H–Obond by different amounts upon being compressed, approaching identicallength of 0.11 nm. The van der Waals potential VL(r) for the O:H noncovalent bond reachesa valley at −0.25 eV, and the lowest exchange VH(r) for the H–O polar-covalentbond is valued at −3.97 eV. [ABSTRACT FROM AUTHOR]