Impurity-Induced Structural Transformation of a MgO Grain Boundary

Abstract

A combination of atomic-resolution $Z$-contrast imaging and first-principles density-functional calculations are used to establish that Ca impurities segregating to particular atomic columns in MgO grain boundaries induce a structural transformation. The presence of Ca in the boundary structure is independently confirmed by electron energy loss spectroscopy. The calculated electronic structure indicates that stabilization of the new boundary structure by Ca is a mechanical rather than an electronic effect.