posted on 2020-03-17, 14:34authored byAndrew B. Cairns, Jadna Catafesta, Patrick Hermet, Jérôme Rouquette, Claire Levelut, David Maurin, Arie van der Lee, Vladimir Dmitriev, Jean-Louis Bantignies, Andrew L. Goodwin, Julien Haines
The
negative thermal expansion material potassium cadmium dicyanoargentate,
KCd[Ag(CN)2]3, is studied at high pressure using
a combination of X-ray single-crystal diffraction, X-ray powder diffraction,
infrared and Raman spectroscopy, and density functional theory calculations.
In common with the isostructural manganese analogue, KMn[Ag(CN)2]3, this material is shown to exhibit very strong
negative linear compressibility (NLC) in the crystallographic c direction due to structure hinging. We find increased
structural flexibility results in enhanced NLC and NTE properties,
but this also leads to two pressure-induced phase transitionsto
very large unit cells involving octahedral tilting and shearing of
the structurebelow 2 GPa. The presence of potassium
cations has an important effect on the mechanical and thermodynamic
properties of this family, while the chemical versatility demonstrated
here is of considerable interest to tune unusual mechanical properties
for application.