  The growing trend towards engineering interfacial complexion (or phase)
transitions has been seen in the grain boundary and solid surface
systems.Meanwhile, little attention has been paid to the chemically
heterogeneous solid/liquid interfaces. In this work, novel in-plane
multi-interfacial states coexist within the Cu(111)/Pb(l) interface at a
temperature just above the Pb freezing point is uncovered using atomistic
simulations.Four monolayer interfacial states, i.e., two CuPb alloy liquids and
two pre-freezing Pb solids, are observed coexisting within two interfacial
layers sandwiched between the bulk solid Cu and bulk liquid Pb. Through
computing the spatial variations of various properties along the direction
normal to the in-plane solid-liquid boundary lines for both interfacial layers,
a rich and varied picture depicting the inhomogeneity and anisotropy in the
mechanical, thermodynamical, and dynamical properties is presented. The bulk
values extracted from the in-plane profiles suggest that each interfacial state
examined has distinct equilibrium values from each other and significantly
deviates from those of the bulk solid and liquid phases, and indicate that the
complexion (or phase) diagrams for the Cu(111)/Pb(l) interface bears a
resemblance to that of the eutectic binary alloy systems, instead of the
monotectic phase diagram for the bulk CuPb alloy. The reported data could
support the development of interfacial complexion (or phase) diagrams and
interfacial phase rules and provide a new guide for regulating heterogeneous
nucleation and wetting processes.
