Mariana Derzsi, Wojciech Grochala, University of Warsaw, Poland, Viktor V. Struzhkin, Carnegie Institution of Washington, Washington, D.C., USA, and colleagues have discovered a high-pressure polymorph of AgF₂. The compound is the first example of a metal fluoride nanowire.

The team subjected AgF₂, which has a crystal structure featuring AgF₄ squares, to pressures above 15 GPa using a diamond anvil cell. The transformation was monitored using powder X-ray diffraction. The researchers found that the layered low-pressure AgF₂ structure was converted to a quasi-1D nanotubular structure, composed of “stacked” square planar AgF₄ units. The nanotubes are densely packed in the crystal lattice, which makes the structure stable at high pressures.

Due to the presence of the strongly electron-deficient Ag(II) cation, the team proposes that the material could have interesting magnetic and electronic properties. Density functional theory (DFT) calculations suggest that polymorph could be stable in a pressure range from ambient up to 80 GPa.

• Metal fluoride nanotubes featuring square-planar building blocks in a high-pressure polymorph of AgF₂,
  A. Grzelak, J. Gawraczyński, T. Jaroń, D. Kurzydłowski, Z. Mazej, P. J. Leszczyński, V. B. Prakapenka, M. Derzsi, V. V. Struzhkin, W. Grochala,
  Dalton Trans. 2017.
  DOI: 10.1039/c7dt03178e