Atomistic simulation of oxide dislocations and interfaces

Atomistic simulation techniques have been used to study screw dislocations, grain boundaries, thin films and surfaces. The results show that the a/2〈110〉 screw dislocations in bulk MgO and NiO are more stable than the a〈100〉 although the latter are stabilised by vacancies. Adsorption of MgO units at the a〈100〉 spiral dislocation shows a complicated two-layer growth mechanism. Self-diffusion through MgO grain boundaries is shown to be faster than in the bulk crystal, with pipe diffusion the energetically most favourable route. Study of thin iron oxide films on MgO found that the most stable MgO/Fe3O4 {001}/(001) interface is an open structure with closely matching spacing between substrate Mg ions and oxygens of the film. The interaction of water with oxides MgO and SiO2 has been investigated. The dominance of the MgO {100} surface is shown through facetting of the less stable {110} and {111} surfaces. The low-coordinated surface sites hence formed are the most reactive towards adsorption of water...