  Targeting specific technological applications requires the control of
nanoparticle properties, especially the crystalline polymorph. Freezing a
nanodroplet deposited on a solid substrate leads to the formation of
crystalline structures. We study the inherent mechanisms underlying this
general phenomenon by means of molecular dynamics simulations. Our work shows
that different crystal structures can be selected by finely tuning the solid
substrate lattice parameter. Indeed, while for our system, face-centered cubic
is usually the most preponderant structure, the growth of two distinct
polymorphs, hexagonal centered packing and body-centered cubic, was also
observed even when the solid substrate was face-centered cubic. Finally, we
also demonstrated that the growth of hexagonal centered packing is conditioned
by the appearance of large enough body-centered cubic clusters thus suggesting
the presence of a cross-nucleation pathway. Our results provide insights into
the impact of nanoscale effects and solid substrate properties towards the
growth of polymorphic nanomaterials.
