Correlation and size dependence of the lattice strain, binding energy, elastic modulus, and thermal stability for Au and Ag nanostructures

Abstract

As a group of wonder materials, gold and silver at the nanoscale demonstrate many intriguing properties that cannot be seen from their bulk counterparts. However, consistent insight into the mechanism behind the fascinations and their interdependence given by one integrated model is highly desirable. Based on Goldschmidt-Pauling’s rule of bond contraction and its extension to the local bond energy, binding energy density, and atomic cohesive energy, we have developed such a model that is able to reconcile the observed size dependence of the lattice strain, core level shift, elastic modulus, and thermal stability of Au and Ag nanostructures from the perspective of skin-depth bond order loss. Theoretical reproduction of the measured size trends confirms that the undercoordination-induced local bond contraction, bond strength gain, and the associated binding energy density gain, the cohesive energy loss and the tunable fraction of such undercoordinated atoms dictate the observed fascinations, which should shed light on the understanding of the unusual behavior of other nanostructured materials as well.