Data set for Fe-Cu-Ni liquid ternary calculations with LAMMPS Output from a series of runs using the FeCuNi.eam.alloy EAM potential with LAMMPS to compute Gibbs free energies. The runs are from 1200K to 3000K in 300K increments, over a variety of concentrations. Chemical potential differences are extracted and analyzed to produce a ternary phase diagram. Nonequilibrium Hamiltonian integration is used to compute absolute Gibbs free energies for the pure liquids.