&60; p&62; Abstract&60;/p&62; &60; p&62; We report on the equilibrium shape and atomic structure of thermally-processed Au nanocrystals (NCs) as determined by high resolution transmission electron microscopy (TEM). The NCs were either deposited on SiO&60; sub&62; 2&60;/sub&62; surface or embedded in SiO&60; sub&62; 2&60;/sub&62; layer. Quantitative data on the NCs surface free energy were obtained via the inverse Wulff construction. Nanocrystals inside the SiO&60; sub&62; 2&60;/sub&62; layer are defect-free and maintain a symmetrical equilibrium shape during the growth. Nanocrystals on SiO&60; sub&62; 2&60;/sub&62; surface exhibit asymmetrical equilibrium shape that is characterized by the introduction of twins and more complex atomic defects above a critical size. The observed differences in the equilibrium shape and atomic structure evolution of growing …