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Core structure of screw dislocations in hcp Ti: an ab initio DFT study

Nathalie Tarrat , Magali Benoit and Joseph Morillo

Abstract

The core structure of screw dislocations in -Ti was studied in the cluster approach with ab initio DFT-GGA, and in both the cluster and quadrupole approaches with a recently highly optimized EAM central force potential. With the EAM potential we have shown that finite-size effects, in the cluster approach, are negligible down to the size studied in the ab initio DFT calculations that have shown unambiguously a preferential prismatic core spreading for the dislocation. Our results are in agreement with previously published approximated calculations using empirical or semi-empirical interaction models: only approximated interaction models, taking explicitly into account the covalent directional bonding of the d electrons, can properly account for the preferential prismatic core spreading against the basal one; and empirical interaction models without angular force components are inadequate. Interestingly, at first sight, the relaxed core structures (basal or prismatic) obtained with empirical or semi-empirical interaction models are almost identical to the ones obtained with the ab initio DFT calculations.


* Correspondence address, Nathalie Tarrat Centre d'Elaboration des Matériaux et d'Etudes Structurales, CNRS (UPR 8011), 29 rue Jeanne Marvig, 31055 Toulouse Cedex 4, France Tel.: +33 562 257 896 Fax: +33 562 257 999 E-mail:

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Received: 2008-8-28
Accepted: 2009-1-12
Published Online: 2013-06-11
Published in Print: 2009-03-01

© 2009, Carl Hanser Verlag, München

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