Ambient-stable tetragonal phase in silvernanostructures

摘要

Crystallization of noble metal atoms usually leads to the highly symmetric face-centredcubic phase that represents the thermodynamically stable structure. Introducing defectivemicrostructures into a metal crystal lattice may induce distortions to form non-face-centeredcubic phases when the lateral dimensions of objects decrease down to nanometre scale.However, stable non-face-centered cubic phases have not been reported in noble metalnanoparticles. Here we report that a stable body-centred tetragonal phase is observed in silvernanoparticles with fivefold twinning even at ambient conditions. The body-centered tetragonalphase originates from the distortion of cubic silver lattices due to internal strains in the twinnednanoparticles. The lattice distortion in the centre of such a nanoparticle is larger than that in thesurfaces, indicating that the nanoparticle is composed of a highly strained core encapsulated ina less-strained sheath that helps stabilize the strained core.