Effect of Eshelby twist on core structure of screw dislocations in molybdenum: atomic structure and electron microscope image simulations

0359531 - ÚFM 2012 RIV GB eng J - Journal Article
Gröger, Roman - Dudeck, K. J. - Nellist, P. D. - Vitek, V. - Hirsch, P. B. - Cockayne, D. J. H.
Effect of Eshelby twist on core structure of screw dislocations in molybdenum: atomic structure and electron microscope image simulations.
Philosophical Magazine. Roč. 91, č. 18 (2011), s. 2364-2381. ISSN 1478-6435. E-ISSN 1478-6443
R&D Projects: GA ČR GAP204/10/0255
Institutional research plan: CEZ:AV0Z20410507
Keywords : screw dislocation * thin foil * Eshelby twist * free surface * HREM
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.510, year: 2011

This paper addresses the question as to whether the core structure of screw dislocations in Mo in the bulk can be obtained from high-resolution electron microscopy (HREM) images of such dislocations viewed end-on in a thin foil. Atomistic simulations of the core structure of screw dislocations in elastically anisotropic Mo were carried out using bond order potentials. They show that the differential displacements of the atoms at the surface are different with components perpendicular to the Burgers vector about five times larger than those in the middle of the foil, the latter being characteristic of the bulk. Nye tensor plots show that the surface relaxation stresses strongly affect the incompatible distortions. HREM simulations of the computed structure reflect the displacements at the exit surface, modified by interband scattering and the microscope transfer function. Nye tensor plots obtained from the HREM images show that interband scattering also affects the incompatible distortions. It is concluded that it would be difficult to obtain the core structure of screw dislocations in the bulk Mo from HREM images, even under ideal experimental conditions.
Permanent Link: http://hdl.handle.net/11104/0197306