  Via molecular dynamics simulations we study ICE formation in the TIP4P/Ice
model that is known to describe structure and dynamics in various phases of
WATER accurately. For this purpose well equilibrated configurations from
different initial temperatures, Ts, belonging to the fluid phase, are quenched
to a fixed subzero temperature. Our results on kinetics, for a wide range of
Ts, following such quenches, show quicker crystallization of samples that are
hotter at the beginning. This implies the presence of the puzzling Mpemba
effect (ME). Via a similar study, we also identify ME in fluid to solid
transitions in a Lennard-Jones (LJ) model. In the latter case, the ME appears
purely as an outcome of the influence of critical fluctuations on the
nonequilibrium growth process, for which we present interesting scaling
results. For the TIP4P/Ice case, on the other hand, we show that delay in
nucleation, due to metastability, can alone be a driving factor for the
exhibition of ME. To substantiate the difference between the two cases, we also
present LJ-like scaling results for ME in a magnetic transition. Our
simulations indicate that in each of the systems the effect can be observed
independent of the cooling rate that may vary when samples from different Ts
are brought in contact with a heat reservoir working at a fixed lower
temperature.
