Mechanics of Gold Nanoparticle Superlattices at High Hydrostatic Pressures

Pressure-driven assembly of ligand-grafted gold nanoparticle superlattices is a promising approach for fabricating gold nanostructures, such as nanowires and nanosheets. Optimizing this fabrication method will require extending our understanding of superlattice mechanics to regimes of high pressures. We use molecular dynamics simulations to characterize the response of alkanethiol-grafted gold nanoparticle superlattices to applied hydrostatic pressures up to 15 GPa. At low applied pressures, intrinsic voids govern the mechanics of compaction. As applied pressures increase, the void collapse and ligand compression depend significantly on the ligand length. These microstructural observations correlate directly with trends in bulk modulus and elastic constants. For short ligands, core-core contact between gold nanoparticles is observed at high pressures, which augurs irreversible response and eventual sintering. This presintering behavior was unexpected under hydrostatic loading and is observed only for the shortest ligands.