posted on 2016-02-16, 00:00authored byPiero Gasparotto, Ali A. Hassanali, Michele Ceriotti
The hydrogen-bond
network of water is characterized by the presence
of coordination defects relative to the ideal tetrahedral network
of ice, whose fluctuations determine the static and time-dependent
properties of the liquid. Because of topological constraints, such
defects do not come alone but are highly correlated coming in a plethora
of different pairs. Here we discuss in detail such correlations in
the case of ab initio water models and show that they have interesting
similarities to regular and defective solid phases of water. Although
defect correlations involve deviations from idealized tetrahedrality,
they can still be regarded as weaker hydrogen bonds that retain a
high degree of directionality. We also investigate how the structure
and population of coordination defects is affected by approximations
to the interatomic potential, finding that, in most cases, the qualitative
features of the hydrogen-bond network are remarkably robust.