Why do compact grain boundary complexions prevail in rock-salt materials?

Over 40 years of studies grain boundaries in ionic rock-salt materials have left the community divided. On one hand, numerical simulations systematically predict open, hollow structural units to be ground state. other, most recent experiments report compact structures norm. To reconcile modelling with experimental evidence, we investigate stability three high-angle symmetric tilt magnesium oxide MgO respect presence charge-neutral vacancy pairs. We demonstrate that although open are energetically favourable, they easily destabilized by vacancies. It follows complexions can never at equilibrium surrounding grains finite temperature. contrary, accommodate a wide range defects concentrations, and much more resilient absorption These results highlight limitations consider only state, stress importance accounting for other when materials.