Atomistic simulation of the effect of impurities on vacancy migration at the {4 1 0}/[0 0 1] tilt grain boundary of MgO

We present the results of atomistic simulations to calculate the effect of impurities on vacancy migration at the {4 1 0} tilt grain boundary of MgO. We show that impurities within the mantle could significantly modify vacancy migration within the mantle due to segregation to grain boundaries. This segregation increases with increasing impurity size and with increasing pressure. The impurities have little effect on vacancy migration at 0 GPa but at higher pressures the impurities alter the activation energies such that the vacancies prefer to migrate towards them. This suggests that at mantle conditions the vacancies will be pinned both by the compression of the boundary and also the impurities, slowing diffusion. Received: 22 February 1999 / Revised, accepted: 1 June 1999