  Grain boundaries have been shown to dramatically influence the behavior of
relatively simple materials such as monatomic metals and binary alloys. The
increased chemical complexity associated with multi-principal element alloys is
hypothesized to lead to new grain boundary phenomena. To explore the
relationship between grain boundary structure and chemistry in these materials,
hybrid molecular dynamics/Monte Carlo simulations of a faceted {\Sigma}11 <110>
tilt boundary, chosen to sample both high- and low-energy boundary
configurations, are performed in face-centered cubic CrFeCoNiCu and CrFeCoNi
equiatomic alloys. Unexpected enrichment of Fe is discovered in the
face-centered cubic regions adjacent to the interface and found to be
correlated with a structurally-distinct region of reduced atomic volume.
Comparison with the boundary of the same type in monatomic Cu demonstrates that
altered near-boundary regions exist in simpler systems as well, with the
chemical complexity of the multi-principal element alloys highlighting its
existence and importance.
