PECULIAR SURFACE SIZE-EFFECTS IN NaCl NANO-CRYSTALS

While the major target of this contribution was the stabilization of the theoretically predicted CsCl form of the sodium chloride which could exhibit a singular and peculiar metallic behavior, this study took advantage of the nano-scaled aspect of the synthesized NaCl to report for the first time in the literature, the size dependence of various thermodynamic parameters of nano-sized NaCl crystals. More accurately, size effect on vaporization temperature of NaCl nano-crystals has been conducted on NaCl nanoparticles exhibiting a net shape anisotropy. The investigated nano-scaled NaCl particles were micrometric in the basal plane while nanometric in the transversal direction. An obvious size variation of the vaporization temperature is observed experimentally in agreement with the theoretical predictions. Specifically, the vaporization temperature TV decreases from almost 1680 (bulk) to 1290 K (nano-sized): a relative decrease of nearly 23.5%. The TV ≈ T(χ) size dependence where χ is the relative molar concentration of the initial NaCl precursor was found to follow the form TV(°C) ≈ 750.7χ2 - 340.1χ + 1002.