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Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids

Stukowski, A. and Markmann, J. and Weissmueller, J. and Albe, K. (2009):
Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids.
In: Acta Materialia, Elsevier Science Publishing Company, pp. 1648-1654, 57, (5), [Online-Edition: http://www.sciencedirect.com/science/article/pii/S1359645408...],
[Article]

Abstract

The origin of microstrain broadening in X-ray diffraction patterns of nanocrystalline metals is investigated by comparing data obtained from Virtual diffractograms and from direct analysis of computer-generated samples. A new method is introduced that allows the local deformation gradient to be calculated for each lattice site in the microstructure from atomic coordinates obtained by molecular dynamics simulations. Our results reveal that microstrain broadening in undeformed samples cannot be attributed to lattice dislocations or strain fields near grain boundaries. The broadening arises, instead. from long-range correlated displacement fields that extend throughout the grains. The microstrain therefore provides a quantitative measure for distortions far from grain boundaries. This suggests that diffraction-based strategies for inferring the dislocation density in ultrafine-grained metals do not necessarily apply to nanocrystalline materials. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Item Type: Article
Erschienen: 2009
Creators: Stukowski, A. and Markmann, J. and Weissmueller, J. and Albe, K.
Title: Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids
Language: English
Abstract:

The origin of microstrain broadening in X-ray diffraction patterns of nanocrystalline metals is investigated by comparing data obtained from Virtual diffractograms and from direct analysis of computer-generated samples. A new method is introduced that allows the local deformation gradient to be calculated for each lattice site in the microstructure from atomic coordinates obtained by molecular dynamics simulations. Our results reveal that microstrain broadening in undeformed samples cannot be attributed to lattice dislocations or strain fields near grain boundaries. The broadening arises, instead. from long-range correlated displacement fields that extend throughout the grains. The microstrain therefore provides a quantitative measure for distortions far from grain boundaries. This suggests that diffraction-based strategies for inferring the dislocation density in ultrafine-grained metals do not necessarily apply to nanocrystalline materials. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Journal or Publication Title: Acta Materialia
Volume: 57
Number: 5
Publisher: Elsevier Science Publishing Company
Uncontrolled Keywords: X-ray diffraction (XRD), Nanocrystalline materials, Grain boundary structure, Molecular dynamics simulations (MD simulations), Microstrain
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Date Deposited: 22 Feb 2012 16:25
Official URL: http://www.sciencedirect.com/science/article/pii/S1359645408...
Identification Number: doi:10.1016/j.actamat.2008.12.01
Related URLs:
Funders: The authors acknowledge the financial support of the Deutsche Forschungsgemeinschaft (FOR714) and the grants for computing time by the Forschungszentrum Jülich and the HHLR in Darmstadt and Frankfurt.
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