Large elastic recovery of zinc dicyanoaurate

We report a single-crystal nanoindentation study of the negative compressibility material zinc(II) dicyanoaurate. The material exhibits a particularly strong elastic recovery, which we attribute to the existence of supramolecular helices that function as atomic-scale springs—storing mechanical energy during compressive stress and inhibiting plastic deformation. Our results are consistent with the relationship noted by Cheng and Cheng [Appl. Phys. Lett. 73, 614 (1998)] between elastic recovery and the ratio of material hardness to Young’s modulus. Drawing on comparisons with other framework materials containing helical motifs, we suggest helices as an attractive design element for imparting resistance to plastic deformation in functional materials.