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Search Publications by: James A. Warren (Fed)

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Displaying 76 - 100 of 181

An Efficient Algorithm for Solving the Phase Field Crystal Model

June 1, 2008
Author(s)
Mowei Cheng, James A. Warren
We present and discuss the development an unconditionally stable algorithm to solving the evolution equations for the Phase Field Crystal (PFC) model. This algorithm allows for an arbitrarily large algorithmic time step. As the basis for our analysis of

Atomic Motion During the Migration of General [001] Tilt Grain Boundaries in Ni

August 24, 2007
Author(s)
Hao Zhang, David J. Srolovitz, Jack F. Douglas, James A. Warren
We generalize a previous study of the atomic motions governing grain boundary migration to consider arbitrary misorientations of [001] tilt boundaries. Our examination of the nature of atomic motions employed three statistical measures: the non-Gaussian

Phase Field Theory of Heterogeneous Crystal Nucleation

January 19, 2007
Author(s)
L Granasy, T Pusztai, D M. Saylor, James A. Warren
A phase field approach is developed to model wetting and heterogeneous crystal nucleation of an undercooled pure liquid in contact with a sharp wall. We discuss various choices for the boundary condition at the wall and determine the properties of critical

Accuracy of Unconditionally Stable Algorithms in Cahn-Hilliard Systems

January 11, 2007
Author(s)
Mowei Cheng, James A. Warren
Given an unconditionally stable algorithm for solving the Cahn-Hilliard equations, we provide the mathematical basis for arbitrary accuracy -- we present a general calculation for an analytical time step Δ Tau in terms of an algorithmic time step Δ Tau. By

Characterization of Atomic Motions Governing Grain Boundary Migration

September 24, 2006
Author(s)
Hao Zhang, David J. Srolovitz, Jack F. Douglas, James A. Warren
Molecular dynamics simulations were employed to study atomic motion within stationary and migrating asymmetric tilt grain boundaries. We employ several measures of the complexity of the atomic trajectories, including the van Hove correlation function, the

Numerical Modeling of Diffusion-Induced Deformation

September 11, 2006
Author(s)
J A. Dantzig, William J. Boettinger, James A. Warren, Geoffrey B. McFadden, Sam R. Coriell, R F. Sekerka
We present a numerical approach to modeling the deformation induced the the Kirkendall effect in binary alloys. The governing equations for isothermal binary diffusion are formulated with respect to inert markers and also with respect to the volume

Polycrystalline Patterns in Far-From-Equilibrium Freezing: A Phase Field Study

August 1, 2006
Author(s)
L Granasy, T Pusztai, T Borzsonyi, G Toth, G -. Tegze, James A. Warren, Jack F. Douglas
We discuss the formation of polycrystalline microstructures with the framework of phase field theory. First, the model is tested for crystal nucleation in a hard sphere system. It is shown that, when evaluating the model parameters from molecular dynamics

Simultaneous Grain Boundary Migration and Grain Rotation

April 11, 2006
Author(s)
M Upmanyu, David J. Srolovitz, A E. Lobkovsky, James A. Warren, W Carter
The energy of a polycrystalline network can be reduced by both grain boundary migration and by grain rotation. We perform a series of molecular dynamics (MD) simulations of a circular grain embedded in an otherwise single crystal matrix and monitor both

Phase-Field Modeling of Solidification Under Stress

January 2, 2006
Author(s)
Julia Slutsker, K Thornton, Alexander Roytburd, James A. Warren, Geoffrey B. McFadden, P W. Voorhees
A phase-field model that includes the stress field during non-isothermal phase transformation of a single-vomponent system has been developed. The model has been applied to the solidification and melting of confined spherical volumes, where sharp interface