ATOMISTIC SIMULATION OF THE EFFECT OF TEMPERATURE AND PRESSURE ON THE[001] SYMMETRICAL TILT GRAIN-BOUNDARIES OF MGO

Computer simulation has been used to model a series of grain boundarie s of MgO. The aim of the work is to establish a procedure for generati ng grain boundaries and to calculate the effect of high pressures and temperatures upon the structure, energies and ultimately diffusivities associated with these boundaries. The simulations predict that temper atures up to 1200 K have little effect upon the structure and energies , whereas pressures of up to 40 GPa have a large effect, causing the f ree energy of formation to increase with pressure for all the grain bo undaries studied. In addition the (310), (410) and (510) grain boundar ies undergo structural changes to minimize the dilation of the grain b oundary. In the case of the (410) and (510) grain boundaries this stru cture change is found to be irreversible when the pressure is released .