title: Ambient-stable tetragonal phase in silver nanostructures.
abstract: Crystallization of noble metal atoms usually leads to the highly symmetric face-centred cubic phase that represents the thermodynamically stable structure. Introducing defective microstructures into a metal crystal lattice may induce distortions to form non-face-centered cubic 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 metal nanoparticles. Here we report that a stable body-centred tetragonal phase is observed in silver nanoparticles with fivefold twinning even at ambient conditions. The body-centered tetragonal phase originates from the distortion of cubic silver lattices due to internal strains in the twinned nanoparticles. The lattice distortion in the centre of such a nanoparticle is larger than that in the surfaces, indicating that the nanoparticle is composed of a highly strained core encapsulated in a less-strained sheath that helps stabilize the strained core.
authors: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA. ygsun@anl.gov
authors: Yugang
authors: Y
authors: Sun
authors: Yang
authors: Y
authors: Ren
authors: Yuzi
authors: Y
authors: Liu
authors: Jianguo
authors: J
authors: Wen
authors: John S
authors: JS
authors: Okasinski
authors: Dean J
authors: DJ
authors: Miller
mesh_terms: D053768:Metal Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D012834:Silver / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D012834:Silver