Direct Visualization of Localized Vibrations At Complex Grain Boundaries.

Grain boundaries (GBs) are a prolific microstructural feature that dominates the functionality of a wide class of materials. The functionality at a GB results from unique atomic arrangements, different from those in the grain, that have driven extensive experimental and theoretical studies correlating atomic-scale GB structures to macroscopic electronic, infrared-optical, and thermal properties. [ 8 ] Here, we examine a SrTiO 3 GB using atomic-resolution aberration-corrected scanning transmission electron microscopy (STEM) and ultrahigh-energy-resolution monochromated electron energy-loss spectroscopy (EELS), in conjunction with density-functional-theory (DFT). This combination enables the correlation of the GB structure, nonstoichiometry, and chemical bonding with a redistribution of vibrational states within the GB dislocation-cores. The new experimental access to localized GB vibrations provides a direct route to quantifying the impact of individual boundaries on macroscopic properties. This article is protected by copyright. All rights reserved.