HR: 0830h
AN: V11D-0527    [PDF]
TI: Modelling the Cores of Dislocations Minerals
AU: * Walker, A M
EM: andreww@ri.ac.uk
AF: Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, W1S 4BS United Kingdom
AU: * Walker, A M
EM: andreww@ri.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Gale, J D
EM: j.gale@ri.ac.uk
AF: Department of Applied Chemistry, Nanochemistry Research Institute, Curtin University of Technology, P.O. Box U1987, Perth, WA 6845 Australia
AU: Slater, B
EM: ben@ri.ac.uk
AF: Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, W1S 4BS United Kingdom
AU: Wright, K
EM: kate@ri.ac.uk
AF: Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, W1S 4BS United Kingdom
AU: Wright, K
EM: kate@ri.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT United Kingdom
AU: Wright, K
EM: kate@ri.ac.uk
AF: Department of Chemistry, Christopher Ingold Laboratories, University College London, 20 Gordon Street, London, WC1H 0AJ United Kingdom
AB: Dislocations influence many properties of minerals, including plastic deformation, growth and dissolution, diffusion and the formation of polytypes. Some of these properties can be understood using concepts based on a description of the mineral as an elastic continuum. However, for those properties where a description of the core is important, such an approach fails and an atomic scale view must be sought. So far atomic scale modelling of the core of dislocations has been restricted to simple cubic materials and metals. We describe a recently developed a protocol for the simulation of the core of dislocations in complex ionic and semi-ionic materials at atomic resolution. The methodology, as implemented in the program GULP [1], involves embedding an atomistic model of the dislocation core, and its immediate surroundings, in a representation of the rest of the crystal based on anisotropic linear elasticity. The simulated system is periodic in 1-dimension and follows from the developments made by, for example, Hoagland {\it et al.} [2], but it is not limited to simple cubic materials. The above methodology is illustrated by reference to applications involving varied mineral systems including upper mantle silicates, simple oxides and topologically more complex materials. These studies throw light on varied aspects of mineralogy, from studies of crystal growth processes associated with the emergence of screw dislocations at the surface of minerals, to the plasticity of minerals in the Earth's mantle. Studies of plasticity and dislocations in mantle minerals have been an active area of experimental science for many years, but this is, we believe, the first systematic attempt to model the core of dislocations in a range of complex ionic systems. [1] Gale, J. D. and A. L. Rohl (2003) {\it The General Utility Lattice Program (GULP).} Molecular Simulations {\bf 29} pp. 291-341. [2] Hoagland, R. G., J. P. Hirth, P. C. Gehlen (1976) {\it Atomic simulation of the dislocation core structure and Peirels stress in alkali halide.} Philosophical Magazine {\bf 34} 413-439.
DE: 3900 MINERAL PHYSICS
DE: 3902 Creep and deformation
DE: 3904 Defects
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting