Researchers reoprt a stable body-centred tetragonal phase in silver nanoparticles

(Nanowerk News) So far, stable non-face-centered cubic phases in noble metal nanoparticles have not been reported yet. 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 nanoscale.
Researchers at Argonne National Laboratory's Center for Nanoscale Materials have now observed a stable body-centred tetragonal phase in silver nanoparticles with fivefold twinning even at ambient conditions. They report their findings in an open-access paper in Nature Communications ("Ambient-stable tetragonal phase in silver nanostructures").
Schematic drawing of a silver nanowire with fivefold symmetry
Schematic drawing of a silver nanowire with fivefold symmetry.
They report that 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.
Source: Argonne National Laboratory