Crystal growth and melting in NiZr alloy: Linking phase-field modeling to molecular dynamics simulations

We compare results from molecular dynamics simulations with those from phase-field modeling concerning the solidification and melting kinetics of a planar ${[{\text{Ni}}_{c}{\text{Zr}}_{1\ensuremath{-}c}]}_{\text{liquid}}{\text{-Zr}}_{\text{crystal}}$ interface. Our study is an illustration that both approaches may predict the same quantitative physical description when the key parameters calculated within the atomistic molecular dynamics approach are used to construct the mesoscopic phase-field model. We show in this way that a thermodynamic consistent phase-field model can be applied down to the range of atomic structure. At the same time, molecular dynamics simulation seems to be capable to treat correctly relaxation dynamics, driven by thermodynamic forces, in a nonequilibrium state of solidification and melting. We discuss, in particular, how the free energy from atomistic calculations is used to design the phase dependent free-energy density in the phase-field model. Bridging the gap between both simulation approaches contributes to a better understanding of the thermodynamic and kinetic processes underlying the solidification and melting processes in alloys out of chemical equilibrium. The effective thermodynamic enhancement of the diffusivity through the strong negative enthalpy of mixing in the NiZr solution is discussed.