Nanocrystalline materials offer very high strength but are typically limited in their strain to failure, and efforts to improve deformability in these materials are usually found to be at the expense of strength. Using a combination of quantitative in situ compression in a transmission electron microscope, the mechanical properties of nanoparticles are directly measured on an individual basis. The computational tools of finite element analysis (FEA) and density functional theory (DFT) are vital for accurately interpreting the experimental data.

Nanocrystalline CdS synthesized into a spherical shell geometry was found to be capable of withstanding extreme stresses (approaching the ideal shear strength of CdS). This unusual strength enables the spherical shells to exhibit considerable deformation to failure.

Data from a large number of experiments was used to construct a failure criteria based on the maximum shear stresses within the spheres. The failure criteria indicates that shear stresses approach 2.2 GPa, making these structures remarkably strong. DFT was used to compute the ideal shear strength of CdS to be 3 GPa. These nanostructures therefore reach stresses that are approximately 70% of their ideal shear strength before failing. The agreement between the theoretical predictions (red triangles) and the experimental measurements (black circles) is remarkable.