Using the molecular dynamics technique we have investigated the mechan
isms by which a metastable Lennard-Jones fluid transforms into a cryst
al and the morphology of the final state produced. The metastable stat
es were created by equilibrating the fluid state at a temperature abov
e the critical temperature then rapidly quenching to a temperature bel
ow the triple-point temperature. The starting densities were chosen so
that the system was in the metastable two-phase region of the phase d
iagram after the quench. Three quite distinct starting densities were
used corresponding to a low-density gas, a critical-density gas and a
gas at a density of a typical liquid. For each of these starting condi
tions, the final state observed consists of crystalline and gaseous re
gions. However, the mechanism by which these states were reached and t
he morphology of the final state was quite distinct in the three cases
studied.