Carrez, P; Walker, AM; Metsue, A; Cordier, P; (2008) Evidence from numerical modelling for 3D spreading of  screw dislocations in Mg2SiO4 forsterite. PHILOS MAG , 88 (16) 2477 - 2485. 10.1080/14786430802363804.
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Computer simulations have previously been used to derive the atomic scale properties of the cores of screw dislocations in Mg2SiO4 forsterite by direct calculation using parameterized potentials and via the Peierls-Nabarro model using density functional theory. We show that, for the  screw dislocation, the parameterized potentials reproduce key features of generalized stacking fault energies when compared to the density functional theory results, but that the predicted structure of the dislocation core differs between direct simulation and the Peierls-Nabarro model. The  screw dislocation is shown to exhibit a low-energy non-planar core. It is suggested that for this dislocation to move its core may need to change structure and form a high-energy planar structure similar to that derived from the Peierls-Nabarro model. This could lead to dislocation motion via an unlocking-locking mechanism and explain the common experimental observation of long straight screw dislocation segments in deformed olivine.
|Title:||Evidence from numerical modelling for 3D spreading of  screw dislocations in Mg2SiO4 forsterite|
|Keywords:||computer modelling, defect structures, dislocations, minerals, PEIERLS-NABARRO MODEL, COMPUTER-SIMULATION, CORE STRUCTURE, LATTICE-DYNAMICS, HIGH-TEMPERATURE, SINGLE-CRYSTALS, OLIVINE, ANISOTROPY, MOTION, WATER|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences|
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