  We report the mechanical properties of the `giant' negative compressibility
material zinc(II) dicyanoaurate, as determined using a combination of
single-crystal nanoindentation measurements and \emph{ab initio} density
functional theory calculations. While the elastic response of zinc
dicyanoaurate is found to be intermediate to the behaviour of dense and open
framework structures, we discover the material to exhibit a particularly strong
elastic recovery, which is advantageous for a range of practical applications.
We attribute this response to the existence of supramolecular helices that
function as atomic-scale springs, storing mechanical energy during compressive
stress and hence inhibiting plastic deformation. Our results are consistent
with the relationship noted in [Cheng \& Cheng, \textit{Appl. Phys. Lett.},
1998, {\textbf{73}}, 614] between the magnitude of elastic recovery, on the one
hand, and the ratio of material hardness to Young's modulus, on the other hand.
Drawing on comparisons with other metal--organic frameworks containing helical
structure motifs, we suggest helices as an attractive supramolecular motif for
imparting resistance to plastic deformation in the design of functional
materials.
