Investigating the structure-property relationships at grain boundaries in MgO using bond-valence pair potentials and multiple scattering analysis

We describe the use of bond-valence analysis to investigate the segregation of calcium atoms at an MgO [001] tilt grain boundary. For small deviations array from the equilibrium metal-oxide bond length, the bond-valence param eter approximates well to a Born-Mayer-type pair potential. Therefore, by s tarting with a structural model determined from an atomic resolution Z-cont rast image, compositional and cation valence state information obtained fro m electron energy loss spectroscopy (EELS) can be incorporated into a compr ehensive model for the grain boundary For the boundary under investigation here, it is found that specific sites for preferential segregation can be i dentified, resulting in 0.3-0.4 monolayers of calcium in the boundary plane .