PNNL

Abstract

Oriented attachment (OA) is a critical, yet poorly understood crystal growth pathway based on the self-assembly of nanocrystals. During OA, solvent-separated particles align and coalesce via forces via forces enabling precise rotation and translation. While prior studies emphasized intragap forces driving crystallographic alignment, the forces enabling uniform stacking and superlattice formation remain unclear. Here, we demonstrate how macroscopic gibbsite mesocrystals emerge from nanoplates guided into staggered positions by directional sliding. Electron microscopy and X-ray scattering reveal the monoclinic superlattice structure, based on nanoplate stacking with a uniform ~50° stagger along the [010] direction. In situ liquid cell TEM captures preferential sliding along the [010] direction, decelerating with increasing particle overlap. Molecular dynamics simulations confirm that sliding along the [010] direction is energetically favorable, and that the energy barrier rises with increasing overlap until correct attachment is achieved. These insights highlight the energy landscape’s role in OA, with implications for material synthesis and hierarchical structure in nature.