Abstract
A series of [001] tilt grain boundaries in TiO2 (rutile) has been studied using a polarizable point ion shell model. The energy as a function of misorientation angle consists of peaks and cusps. Cusps occur at the (230), (120), (130) and (150) interfaces and others correspond to peaks. Especially the (120) and (230) boundaries have low energies. The (001) projections of calculated equilibrium configurations of these boundaries are also shown. The rutile structure makes these boundaries quite different from the interfaces in NiO which has a simple structure (rock salt) compared with rutile. The results obtained are discussed in terms of monopole fields acting on ions and also the reciprocal density of coincidence sites of ions (Σ). It is found that boundaries with Σ-values smaller than 39 correspond to cusps in the diagram of energy versus misorientation angle, while peaks comprise of boundaries which have large values over 51 for Σ. This fact suggests that the boundary energy is related directly to the reciprocal density of coincidence sites in the case of TiO2.
