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# Prediction of Dislocation Nucleation During Nanoindentation by the Orbital-Free Density Functional Theory Local Quasi-continuum Method

Hayes, Robin L. and Fago, Matt and Ortiz, Michael and Carter, Emily A. (2005) Prediction of Dislocation Nucleation During Nanoindentation by the Orbital-Free Density Functional Theory Local Quasi-continuum Method. Multiscale Modeling and Simulation, 4 (2). pp. 359-389. ISSN 1540-3459 http://resolver.caltech.edu/CaltechAUTHORS:HAYmms05

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## Abstract

We introduce the orbital-free density functional theory local quasi-continuum\linebreak (OFDFT-LQC) method: a first-principles-based multiscale material model that embeds OFDFT unit cells at the subgrid level of a finite element computation. Although this method cannot address intermediate length scales such as grain boundary evolution or microtexture, it is well suited to study material phenomena such as continuum level prediction of dislocation nucleation and the effects of varying alloy composition. The model is illustrated with the simulation of dislocation nucleation during indentation into the $(111)$ and $(\overline{1}10)$ surfaces of aluminum and compared against results obtained using an embedded atom method interatomic potential. None of the traditional dislocation nucleation criteria (Hertzian principal shear stress, actual principal shear stress, von Mises strain, or resolved shear stress) correlates with a previously proposed local elastic stability criterion, $\Lambda$. Discrepancies in dislocation nucleation predictions between OFDFT-LQC and other simulations highlight the need for accurate, atomistic constitutive models and the use of realistically sized indenters in the simulations.

Item Type: Article ©2005 Society for Industrial and Applied Mathematics Received by the editors September 27, 2004; accepted for publication (in revised form) January 25, 2005; published electronically June 27, 2005. This work was supported by DOD-MURI and DOD-ASCI programs. We are grateful to the U.S. Department of Defense for support through Brown University’s MURI Center for the “Design and Testing of Materials by Computation: A Multi-Scale Approach,” the U.S. Department of Energy through Caltech’s ASCI/ASAP Center for the Simulation of the Dynamic Response of Solids, Ron Miller and Ellad Tadmor [45] for providing the EAM code, and Accelrys, Inc. for providing the CASTEP software. multiscale modeling; indentation; dislocation nucleation; embedded atom method; density functional theory CaltechAUTHORS:HAYmms05 http://resolver.caltech.edu/CaltechAUTHORS:HAYmms05 http://dx.doi.org/10.1137/040615869 DOI No commercial reproduction, distribution, display or performance rights in this work are provided. 4514 CaltechAUTHORS Archive Administrator 25 Aug 2006 26 Dec 2012 08:59

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