  We have employed molecular dynamics simulations based on the TIP4P/2005 water
model to investigate the local structural, dynamical, and dielectric properties
of the two recently reported body-centered-cubic and face-centered-cubic
plastic crystal phases of water. Our results reveal significant differences in
the local orientational structure and rotational dynamics of water molecules
for the two polymorphs. The probability distributions of trigonal and
tetrahedral order parameters exhibit a multi-modal structure, implying the
existence of significant local orientational heterogeneities, particularly in
the face-centered-cubic phase. The calculated hydrogen bond statistics and
dynamics provide further indications of the existence of a strongly
heterogeneous and rapidly interconverting local orientational structural
network in both polymorphs. We have observed a hindered molecular rotation,
much more pronounced in the body-centered-cubic phase, which is reflected by
the decay of the fourth-order Legendre reorientational correlation functions
and angular Van Hove functions. Molecular rotation, however, is additionally
hindered in the high-pressure liquid compared to the plastic crystal phase. The
results obtained also reveal significant differences in the dielectric
properties of the polymorphs due to the different dipolar orientational
correlation characterizing each phase.
