  Atomistic simulations are used to study segregation-induced intergranular
film formation in Cu-Zr and Cu-Nb alloys. While Cu-Zr forms structurally
disordered or amorphous films, ordered films comprised of a second phase
usually precipitate in Cu-Nb, with a critical nucleation size of ~1 nm below
which the ordered phase cannot form. While the ordered film is retained at high
temperature for a low energy {\Sigma}11 (113) boundary, a disordering
transition is observed for a high energy {\Sigma}5 (310) boundary at low dopant
concentrations. Finally, the effect of free surfaces on dopant segregation and
intergranular film formation is investigated for both alloys.
