  To understand the effects of lattice mismatch on heteroepitaxial growth, we
have studied the equilibrium structure and orientation relationships (ORs) of
FCC films grown epitaxially on FCC substrates, using molecular dynamics
simulations in conjunction with embedded atom method potentials. Three
film/substrate systems have been investigated, namely: Ag on Cu, Ag on Ni and
Pb on Al. These systems cover a significant range of lattice mismatch, from
12.6% for Ag/Cu to 21.8% for Pb/Al. For each system, the ORs of films on six
different substrate orientations, namely: (100), (511), (311), (211), (322) and
(111), have been investigated. Films on these susbstrates cover a gradual
transition from the oct-cube orientation relationship, which occurs only on
(100) substrates, to the heterotwin orientation relationship, which often
occurs on (111) substrates. It is found that the resulting ORs vary
systematically with substrate orientation, but that the pattern of variation is
almost identical for all three systems, and therefore largely independent of
mismatch. However, the manner in which mismatch is accommodated does depend on
the magnitude of mismatch. Simulations point to an important role for
edge-to-edge matching and defects such as stacking faults. An analysis of these
results in terms of transformation strains highlights the distinction between
the ORs, which are largely independent of mismatch, and the local interfacial
structure, which changes directly with mismatch.
