Abstract
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•This work establishes a novel theory that predicts the inconsistent measurements of the surface free energy of metallic nanoparticles reported by many researchers.•The calculations were compared with the available measurements in the literature for spherical and non-spherical nanoparticles.•The theory predicts that the variation of the surface free energy is attributed to the mutual variation of the size and shape of a nanoparticle.•As a result, it establishes a way to control the mechanical properties of metallic nanoparticles.
We report on the development of an efficient and simple method to calculate the surface free energy (surface tension) of a general-shaped metallic nanosolid. Both nanoparticles and nanostructures that account for the crystal structure and size were considered. The surface free energy of a face-centered cubic structure of a metallic nanoparticles was found to decrease as the size decreases, for a shape factor equal to 1.0 (i.e., spherical). However, when the shape factor exceeds this value, which includes disk-like, regular tetrahedral, regular hexahedral, regular octahedral, nanorod, and regular quadrangular structures, the behavior of the surface free energy was found to reverse, especially for small nanoparticles and then increases as the size decreases. Moreover, this behavior was systematically recorded for large nanoparticles when the mechanical distortion was appreciable. As a matter of fact, this model was also applied to the noble transition metals, including gold and silver nanoparticles. This work is a clear step forward establishing a systematic mechanism for controlling the mechanical properties of nanoscale particles by controlling the shape, size and structure.