  We present a phase diagram for water confined to cylindrical silica nanopores
in terms of pressure, temperature and pore radius. The confining cylindrical
wall is hydrophilic and disordered, which has a destabilizing effect on ordered
water structure. The phase diagram for this class of systems is derived from
general arguments, with parameters taken from experimental observations and
computer simulations and with assumptions tested by computer simulation. Phase
space divides into three regions: a single liquid, a crystal-like solid, and
glass. For large pores, radii exceeding 1 nm, water exhibits liquid and
crystal-like behaviors, with abrupt crossovers between these regimes. For small
pore radii, crystal-like behavior is unstable and water remains amorphous for
all non-zero temperatures. At low enough temperatures, these states are
glasses. Several experimental results for supercooled water can be understood
in terms of the phase diagram we present.
