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Title: Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure: I. Transitions in the one-phase liquid region
Authors: Toth, GI
Granasy, L
Keywords: Density-functional theory
Transmission electron-microscopy
Parabolic free-energy
Lennard-Jones system
Cahn-Hilliard theory
Polycrystalline solidification
Dentritic solidification
Homogeneous nucleation
Publication Date: 2007
Publisher: American Institute of Physics
Citation: Journal of Chemical Physics 127(7): 074709, Aug 2007
Abstract: The phase field theory (PFT) has been applied to predict equilibrium interfacial properties and nucleation barrier in the binary eutectic system Ag-Cu using double well and interpolation functions deduced from a Ginzburg-Landau expansion that considers fcc (face centered cubic) crystal symmetries. The temperature and composition dependent free energies of the liquid and solid phases are taken from CALculation of PHAse Diagrams-type calculations. The model parameters of PFT are fixed so as to recover an interface thickness of approximately 1 nm from molecular dynamics simulations and the interfacial free energies from the experimental dihedral angles available for the pure components. A nontrivial temperature and composition dependence for the equilibrium interfacial free energy is observed. Mapping the possible nucleation pathways, we find that the Ag and Cu rich critical fluctuations compete against each other in the neighborhood of the eutectic composition. The Tolman length is positive and shows a maximum as a function of undercooling. The PFT predictions for the critical undercooling are found to be consistent with experimental results. These results support the view that heterogeneous nucleation took place in the undercooling experiments available at present. We also present calculations using the classical droplet model classical nucleation theory (CNT) and a phenomenological diffuse interface theory (DIT). While the predictions of the CNT with a purely entropic interfacial free energy underestimate the critical undercooling, the DIT results appear to be in a reasonable agreement with the PFT predictions.
Description: The published version of this Article can be accessed from the link below - Copyright @ 2007 American Institute of Physics
Sponsorship: This work has been supported by the Hungarian Academy of Sciences under Contract No. OTKA-K-62588 and by the ESA PECS Contract Nos. 98005, 98021, and 98043.
ISSN: 0021-9606
Appears in Collections:Brunel Centre for Advanced Solidification Technology (BCAST)

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