Effects of Size and Shape on the Tolerances for Misalignment and Probabilities for Successful Oriented Attachment of Nanoparticles

Abstract

Oriented attachment (OA) of nanoparticles is an important pathway of crystal growth, but there is a lack of tools to model OA. Here, we present several simple models that relate the probability of achieving OA to basic geometric parameters, such as particle size, shape, and lattice periodicity. A Moire-domain model is applied to understand twist misorientations between parallel surfaces, and it predicts that the range of twist angles yielding perfect OA is inversely related to the width of the contact area. This idea is explored further through a surface functional model, which investigates how patterns of crystallographic registration can drive the emergence of complex orientational energy landscapes. The energy landscapes are predicted to possess multiple local minima that can trap particles in imperfect alignments, and these local minima become deeper and more numerous as the contact area increases, which makes OA more challenging for large particles. A second set of models is presented to understand the sequence of events by which two crystallographic faces become coplanar after the collision. We use a central force approximation to predict the odds that two particle faces will attain coalignment when the particles collide with random misalignments, and we show that in the absence of special biasing forces, the probability of attaining alignment on a given face is roughly proportional to its solid angle as viewed from the center of the particle. The model thus predicts that OA is most favorable between well-faceted particles and becomes exceedingly unlikely for large spherical particles that express many microfacets.

In Situ TEM Tracking of Disconnection Motion and Atomic Cooperative Reorientation in the Oriented Attachment of Pt Nanoparticles

“…OA involves the coalescence of crystallographically oriented discrete particles followed by interfacial elimination. It typically involves three steps: the collision and rotation of adjacent NPs, the attachment of NPs causing the formation of larger particles, and further recrystallization and interface relaxation. ,,− As initial NPs usually have rough surfaces and different shapes, the alignment during the first step is not always perfect when two crystals aggregate. − Several studies have observed incomplete OA, in which the particles did not fully correct for misalignment during the OA, and the resulting interface consists of GB dislocations. , Molecular dynamics simulations have provided new insights into the dynamics related to OA. Coherent defect-free bonding occurs when the lattices of two nanocrystals join within a critical angle (∼15°), while defects form at the interface when this critical angle is exceeded .…”