title: Step Coalescence by Collective Motion at an Incommensurate Grain Boundary.
abstract: Using extended time series scanning transmission electron microscopy, we investigate structural fluctuations at an incommensurate grain boundary in Au. Atomic-resolution imaging reveals the coalescence of two interfacial steps, or disconnections, of different height via coordinated motion of atoms along close-packed directions. Numerical simulations uncover a transition pathway that involves constriction and expansion of a characteristic stacking fault often associated with grain boundaries in face-centered cubic materials. It is found that local atomic fluctuations by enhanced point defect diffusion may play a critical role in initiating this transition. Our results offer new insights into the collective motion of atoms underlying the lateral advance of steps that control the migration of faceted grain boundaries.
authors.affiliation: Molecular Foundry, National Center for Electron Microscopy, LBNL, Berkeley, California 94720, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Bowers
authors.affiliation: Molecular Foundry, National Center for Electron Microscopy, LBNL, Berkeley, California 94720, USA.
authors.forename: C
authors.initials: C
authors.lastname: Ophus
authors.affiliation: Molecular Foundry, National Center for Electron Microscopy, LBNL, Berkeley, California 94720, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gautam
authors.affiliation: Université Grenoble Alpes, 38042 Grenoble, France, and INAC, SP2M, L_sim, CEA, 38054 Grenoble, France.
authors.forename: F
authors.initials: F
authors.lastname: Lançon
authors.affiliation: Molecular Foundry, National Center for Electron Microscopy, LBNL, Berkeley, California 94720, USA.
authors.forename: U
authors.initials: U
authors.lastname: Dahmen