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Ramalingam, H.B.; Asta, Mark; Walle, Axel van de; Hoyt, J. J.

doi:10.1023/a:1015889313170

Cited by 63 publications

(29 citation statements)

References 19 publications

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“…The chemical part of our model has been tested against atomistic simulations for the Cu-Ni system: The parameter free GL predictions for the order-parameter and nanoscale concentration profiles are in a remarkable agreement with the Monte Carlo results [15] (Fig. 1).…”

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confidence: 65%

Ginzburg-Landau-Type Multiphase Field Model for Competing fcc and bcc Nucleation

2011

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We address crystal nucleation and fcc-bcc phase selection in alloys using a multi-phase-field model that relies on Ginzburg-Landau free energies of the liquid-fcc (face centered cubic), liquid-bcc (body centered cubic), and fcc-bcc sub-systems, and determine the properties of the nuclei as a function of composition, temperature and structure. With a realistic choice for the free energy of the fcc-bcc interface, the model predicts well the fcc-bcc phase-selection boundary in the Fe-Ni system. PACS numbers: 64.60. 64.60.My, 82.60.NFreezing of undercooled liquids often starts with the nucleation/formation of metastable (MS) crystalline phases. In agreement with Ostwald's step rule, atomistic simulations imply that the first crystal structure to form is the one, whose free energy is the closest to the free energy of the liquid [1]. In alloys this represents a multiphase multi-component solidification problem. To date, the most efficient method used for addressing such problems is the multi-phase-field theory (MPFT) [2]. It is, however, only as accurate as the free energy functional it relies on. Early versions [2] of the MPFT predicted that the third phase inevitably appears at the interface between two bulk phases, a behavior originating from the specific free energy surface assumed. A recent version of MPFT eliminated the third phase entirely at the interface [3]. This is not always in agreement with real systems: Atomistic simulations for the Lennard-Jones (LJ) system show that although the stable phase is fcc, small nuclei have a bcc structure, and even the larger fcc crystallites have a bcc-like layer at the solid-liquid interface [1,4], results also born out by the classical density functional theory (CDFT) [5]. These findings accord with the theoretical prediction of Alexander and McTague that in simple liquids the formation of bcc structure is preferred [6]. Further simulations for the LJ system imply that varying the pressure at fixed temperature, the bcc/fcc phase ratio can be tuned in small clusters [7]. Since preference for MS phase nucleation is quite general, it is desirable to work out microscopic models that can handle the structural aspects of phase selection during nucleation.In this Letter, we present such a microscopic model for competing fcc and bcc structures. The MPFT is supplemented with a free energy that is based on the GL expansion of the two-phase free energies [8][9][10], and considers thus the structural aspects of multiphase solidification. Our approach is unique in that it combines crystal structure with thermodynamic and interfacial data of real systems. In this respect our MPFT is more flexible than recent CDFT approaches [11], which, in turn, provide a more detailed description of the solid-solid interface. Herein, we apply the GL-free-energy based MPFT to predict phase-selection in the Fe-Ni system.The standard MPFT form of the grand free energy of a binary system relative to the initial liquid is:(1) The differential operator on the right hand side has the required symmetries [2...

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confidence: 65%

Ginzburg-Landau-Type Multiphase Field Model for Competing fcc and bcc Nucleation

2011

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“…Detailed studies of crystal-melt interface structures have been undertaken for alloy systems based on hard-sphere [329][330][331][332] and Lennard-Jones potentials [333,334], and EAM potentials for Cu [335], an Ni-Cu alloy [336] and the Cu-Ag system [337]. Equilibrium solute and solvent density profiles have been calculated, and the magnitudes of relative solute adsorption coefficients have been computed to have values on the order of a few percent per interface site or less in most cases [330,[332][333][334]336,337] (a notable exception was found in Ref.…”

Section: Structure and Thermodynamics Of Solid-liquid Interfacesmentioning

confidence: 99%

Atomistic modeling of interfaces and their impact on microstructure and properties

2010

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Atomic-level modeling of materials provides fundamental insights into phase stability, structure and properties of crystalline defects, and to physical mechanisms of many processes ranging from atomic diffusion to interface migration. This knowledge often serves as a guide for the development of mesoscopic and macroscopic continuum models, with input parameters provided by atomistic models. This paper gives an overview of the most recent developments in the area of atomistic modeling with emphasis on interfaces and their impact on microstructure and properties of materials. Modern computer simulation methodologies are discussed and illustrated by several applications related to thermodynamic, kinetic and mechanical properties of materials. Existing challenges and future research directions in this field are outlined.

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“…1 appears in the Gibbs adsorption theorem as the partial derivative of g with respect to the chemical potential of the solute; appreciable values of this coefficient would thus represent a source of nontrivial composition dependencies for g. Further evidence for the lack of pronounced equilibrium adsorption for solid-liquid interfaces in simple-metal systems was provided by the work on EAM Ni-Cu alloys performed by Ramalingam et al [115].…”

Section: Binary Alloysmentioning

confidence: 99%

“…10 and 11 show density and composition profiles across {1 0 0} and {1 1 1} solid-liquid interfaces in a Ni-Cu alloy derived from the Monte Carlo studies of Ramalingam et al [115]. In Fig.…”

Section: Binary Alloysmentioning

confidence: 99%

“…Recently, Asta et al [57] demonstrated the application of the CFM to the study of interfacial free energies in Ni-Cu alloys. At a temperature 70 K below the melting point of the solvent (Ni), Monte Carlo was used to equilibrate solid-liquid interface cells following the approach outlined by Ramalingam et al [115]. These cells were then used as the starting point for MD simulations from which the statics and dynamics of interface capillary fluctuations were studied.…”

Section: Binary Alloysmentioning

confidence: 99%

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