  We study the kinetics of vapor-liquid and vapor-solid phase separation of a
hydrodynamics preserving three-dimensional one component Lennard Jones system
in the presence of external gravitational field using extensive molecular
dynamic simulation. A bicontinuous domain structure is formed when the
homogeneous system near the critical density is quenched inside the coexistence
region. In the absence of gravity, the domain morphology is statistically
self-similar and the length scale grows as per the existing laws. However, the
presence of gravity destroys the isotropy of the system and affects the scaling
laws. We observe an accelerated domain growth in the direction of the field at
late time which resembles sedimentation process. Consequently, a new length
scale emerges which strongly depends on the field strength. Similar behavior is
observed in the direction perpendicular to the applied field, with a different
growth rate. Finally, the validity of Porod's law and Superuniversality in such
anisotropic systems is verified in terms of two-point equal time order
parameter correlation function and static structure factor.
