  This note studies Navier-Stokes-Allen-Cahn models for compressible fluids
that are mixtures of two incompressible phases whose density ratio
eps=rho_1/rho_2 is very small. Under a natural assumption on the mixing energy,
it shows the existence of diffuse planar phase boundaries for all 0=eps<eps_0.
For eps=0, one recovers the Navier-Stokes-Korteweg model and its well-known
diffuse phase boundaries.
