Giant negative linear compressibility in zinc dicyanoaurate

The counterintuitive phenomenon of negative linear compressibility (NLC) is a highly desirable but rare property exploitable in the development of artificial muscles1, actuators2 and next-generation pressure sensors3. In all cases, material performance is directly related to the magnitude of intrinsic NLC response. Here we show the molecular framework material zinc(II) dicyanoaurate(I), Zn[Au(CN)2]2, exhibits the most extreme and persistent NLC behaviour yet reported: under increasing hydrostatic pressure its crystal structure expands in one direction at a rate that is an order of magnitude greater than both the typical contraction observed for common engineering materials4 and also the anomalous expansion in established NLC candidates3. This extreme behaviour arises from the honeycomb-like structure of Zn[Au(CN)2]2 coupling volume reduction to uniaxial expansion5, and helical Au...Au 'aurophilic' interactions6 accommodating abnormally large linear strains by functioning as supramolecular springs.