Abstract
simple and general method has been developed to calculate the surface free energy of crys-talline tungsten nanoparticles [NP] and nanostruc-tures [NS]. The model takes into account the size, structure, and shape of nanosolids (NPs/NSs). The size-dependent volume and surface-packing fractions are also considered. Both NPs and NSs show size, structure, and shape dependence of the surface free energy (SFE, ?? ). ?? decreases as the size decreases for spherical NP. As the shape is deformed from spheri-cal, ?? shows opposite behaviors for NPs and NSs, where it increases for NSs. The model also suggests a novel, theoretical method to predict the structural transition in elements from BCC to FCC or vice versa. As a study case, the model has been applied to tungsten (W). The SFE of a W spherical NP of 0.192 eV/& Aring;(2) has been found to drop to 0.150 eV/& Aring;(2) at ultrasmall size for both FCC and BCC. On the other hand, the SFE increases to values ranging between 0.18 to 0.20 eV/& Aring;(2) for shape deformation factors ranging between 1.512 and 2.936. The results were compared with previous theoretical predictions for other transition metals and show a complete agree-ment with the general behavior of this study for tung-sten spherical and non-spherical nano-tungsten.