RheoMan: a five-year, ERC-funded (Advanced Grant), project to model the rheology of the Earth's mantle

Sep 11, 2014 Invited contribution of S. Ritterbex at E-MRS General

On Monday september 15th at 4 pm, Sebastian Ritterbex will give an invited presentation (40 min) at the European Materials Research Society (E-MRS, in Warsaw, Poland) meeting in the symposium « Computer modelling in nanoscience and nanotechnology: an atomic-scale perspective III »

E-MRS 2014 FALL MEETING
Warsaw University of Technology,
Poland

 

Modelling dislocation mobility of complex silicates in the Earth's mantle

Authors : S.Ritterbex, Ph. Carrez, K. Gouriet, P. Cordier

Affiliations : University Lille1

Resume : Mantle convection is the fundamental process by which the Earth expels its internal heat and which drives plate tectonics. It is controlled at the microscopic scale by plastic deformation of solid-state high-pressure phases present in the mantle. Computational materials science is a promising approach to describe and model the fundamental deformation mechanisms operating in the extreme conditions of the deep Earth. Here we study dislocations in two high-pressure polymorphs of Mg2SiO4 stable at 15 to 20 GPa respectively. The Peierls-Nabarro-Galerkin model is used to predict the dislocation structures of both phases integrating the non-elastic nature of the core by atomic scale DFT based calculations. The onset of dislocation mobility at high temperatures is related to thermally activated nucleation of kink-pairs. The original contribution of the present work is to elaborate this model for dissociated dislocations as they occur in these phases. This allows us to predict the critical activation enthalpy required to overcome lattice friction. The model suggests the possibility of different kink-pair mechanisms for dissociated dislocations as a function of applied stress. The effective glide velocity is exponentially related to the critical kink-pair nucleation enthalpy and is used to formulate a constitutive relation appropriate to this mechanism. This couples the fundamental properties of defects in complex silicates and a deformation process active in the Earth's interior.