  A combination of the extended Ice Rule of Pauling, Raman spectroscopy, and
molecular dynamics calculations has enabled us to clarify the bonding origin of
the anomalous volume expansion, Raman phonon relaxation, and the stiffness and
fragility of H2O upon frozen. We found that the initially shorter-and-stronger
intramolecular "H+/p-O2-" bond follows the regular rule of cooling-contraction
while the initially longer-and-weaker intermolecular "O2- : H+/p" nonbond turns
to be even longer yet stiffer in the "O2- : H+/p-O2-" hydrogen-bond of H2O upon
frozen, as a consequence of the polarization and Coulomb repulsion between the
unevenly-bounded bonding and nonbonding electron pairs. The elongation of the
nonbond and the polarization of the nonbonding lone pair are responsible,
respectively, for the volume expansion and the stiffness and the fragility of
ice. Findings should form important impact to the understanding of the physical
anomalies of H2O under other stimuli such as pressure and confinement.
