Surface reconstruction in core@shell nanoalloys: Interplay between size and strain

Shell structure in core@shell nanoalloys is studied where the core comprises of smaller atoms and cov-ered by a thin shell with larger atoms. Mismatch strain, due to the size difference between core and shell atoms, plays a key role in determining the shell arrangement. Binary alloy systems having a wide range of lattice mismatch are considered which include Ni-Ag, Co-Ag, Cu-Ag, Co-Pt, Ni-Pd, Rh-Au, and Ni-Cu. Beginning from very small sizes, transformations in the shell structure are sketched out up to large sizes of similar to 12 nm. These changes are accompanied by reconstruction of {100} facets in the shell to pseudo hexagonal (p-Hex) surfaces. Results show that p-Hex reconstruction occurs in specific size windows. The stability regime and the fraction of p-Hex surfaces is strongly dependent on the lattice mismatch. Com-parison of p-Hex and {111} surfaces reveal significant atomic pressure differences. Finally, shells that are thicker than a monolayer are considered and it is found that p-Hex reconstruction is favored in thicker shells as well. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the shell structure in core@shell nanoalloys, where the core is composed of smaller atoms and covered by a thin shell of larger atoms. The mismatch strain caused by the size difference between the core and shell atoms plays a crucial role in determining the arrangement of the shell. Binary alloy systems with various lattice mismatches are considered, and it is found that the shell structure undergoes transformations accompanied by the reconstruction of {100} facets into pseudo hexagonal (p-Hex) surfaces. The stability regime and the fraction of p-Hex surfaces are strongly influenced by the lattice mismatch. Comparison between p-Hex and {111} surfaces reveals significant differences in atomic pressure. Furthermore, it is observed that p-Hex reconstruction is favored in thicker shells as well.