Abstract
The size effect of materials on the phase structure has been proved by many experiments, and here for the first time, we proposed a size-temperature phase diagram of gallium (Ga). We found that liquid Ga as well as its solid-liquid phase transition (PT) is size dependent. This PT phenomenon was successfully explained in terms of nucleation theory. The size-temperature phase diagram offered a universal phenomenological explanation for the size-related phase selection of Ga. This finding would enrich the general knowledge about the new phenomena induced by the finite-size effect.