  Motivated by recent experiments showing the promise of noble gases as
cryoprotectants, we perform molecular dynamics modeling of phase transitions in
water with xenon under cooling. We study the structure and dynamics of xenon
water solution as a function of temperature. Homogeneous nucleation of
clathrate hydrate phase is observed and characterized. As the temperature is
further reduced we observe hints of dissociation of clathrate due to stronger
hydrophobic hydration, pointing towards a possible instability of clathrate at
cryogenic temperatures and conversion to an amorphous phase comprised of "xenon
+ hydration shell" Xe$\cdot$(H$_{2}$O)$_{21.5}$ clusters. Simulations of
ice$-$xenon solution interface in equilibrium and during ice growth reveal the
effects of xenon on the ice$-$liquid interface, where adsorbed xenon causes
roughening of ice surface but does not preferentially form clathrate. These
results provide evidence against the ice-blocker mechanism of xenon
cryoprotection.
