  Structure and dynamics of water remain a challenge. Resolving the properties
of hydrogen bonding lies at the heart of this puzzle. Here we employ ab initio
Molecular Dynamics (AIMD) simulations over a wide temperature range. The total
simulation time was approx 2 ns. Both bulk water and water in the presence of a
small hydrophobic molecule were simulated. We show that large-angle jumps and
bond bifurcations are fundamental properties of water dynamics and that they
are intimately coupled to both local density and hydrogen bond stretch
oscillations in scales from about 60 to a few hundred femtoseconds: Local
density differences are the driving force for bond bifurcations and the
consequent large-angle jumps. The jumps are intimately connected to the
recently predicted energy asymmetry. Our analysis also appears to confirm the
existence of the so-called negativity track provided by the lone pairs of
electrons on the oxygen atom to enable water rotation.
