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Modelling diffusion in crystals under high internal stress gradients

Olmsted, David L. and Phillips, Rob and Curtin, W. A. (2004) Modelling diffusion in crystals under high internal stress gradients. Modelling and Simulation in Materials Science and Engineering, 12 (5). pp. 781-797. ISSN 0965-0393. doi:10.1088/0965-0393/12/5/003.

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Diffusion of vacancies and impurities in metals is important in many processes occurring in structural materials. This diffusion often takes place in the presence of spatially rapidly varying stresses. Diffusion under stress is frequently modelled by local approximations to the vacancy formation and diffusion activation enthalpies which are linear in the stress, in order to account for its dependence on the local stress state and its gradient. Here, more accurate local approximations to the vacancy formation and diffusion activation enthalpies, and the simulation methods needed to implement them, are introduced. The accuracy of both these approximations and the linear approximations are assessed via comparison to full atomistic studies for the problem of vacancies around a Lomer dislocation in Aluminium. Results show that the local and linear approximations for the vacancy formation enthalpy and diffusion activation enthalpy are accurate to within 0.05 eV outside a radius of about 13 Å (local) and 17 Å (linear) from the centre of the dislocation core or, more generally, for a strain gradient of roughly up to 6 × 10^6 m^-1 and 3 × 10^6 m^-1, respectively. These results provide a basis for the development of multiscale models of diffusion under highly non-uniform stress.

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Phillips, Rob0000-0003-3082-2809
Additional Information:© 2004 IOP Publishing Ltd Received 22 July 2003, Published 1 July 2004, Print publication: Issue 5 (September 2004) The authors gratefully acknowledge support of this work from the US Air Force Office of Scientific Research through the MURI program ‘Virtual Design and Testing of Materials: a Multiscale Approach’, grant #F49620-99-1-0272, and by General Motors through the GM/Brown Collaborative Research Laboratory for Computational Materials Research. The authors also thank Laurent Dupuy for helpful comments on a draft of this paper, Professor Emily Carter at UCLA for providing the saddle point code, Stephen M Foiles and Murray S Daw for developing DYNAMO, and Professor Ron Miller for modifications to the DYNAMO code. An erratum for this article has been published in 2005 Modelling Simul. Mater. Sci. Eng. 13 159-161. The Modelling and Simulation in Materials Science and Engineering publishing team would like to apologize to the authors of the above paper. Due to an oversight, the article was printed in issue 5 of volume 12 without the colour figures requested by the authors. We are therefore reprinting figures 4, 5 and 6 from that article in colour.
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Deposited On:09 Feb 2006
Last Modified:08 Nov 2021 19:12

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