Superheating in metal nanoparticles with non-melting surfaces

We construct microcanonical caloric curves for aluminium nanoparticles with non-melting surface facets and diameters of up to 11 nm using molecular dynamics simulations. We find that fcc aluminium particles can be superheated above the bulk melting temperature, but only for a finite range of particle sizes i.e. diameters between 5–9 nm. We also observe a critical particle size where solid-liquid phase coexistence becomes stable, and a second larger critical size where premelted (100) facets can coexist with solid (111) facets. Ultimately, it is the premelting of the (100) facets that appears to limit the superheating effect in these particles.