Thermodynamic Properties of Supported and Embedded Metallic Nanocrystals: Gold on/in SiO₂

• Main Authors: Giannazzo F, Roccaforte F, Raineri V, Ruffino F, Grimaldi MG
• Format: Article
• Language: English
• Published: SpringerOpen 2008-01-01
• Series: Nanoscale Research Letters
• Subjects: Nanocrystal; Surface energy; Gold; SiO₂; Cohesive energy; Melting temperature; Vacancy formation energy
• Online Access: http://dx.doi.org/10.1007/s11671-008-9180-y
• ISSN: 1931-7573; 1556-276X

<p>Abstract</p> <p>We report on the calculations of the cohesive energy, melting temperature and vacancy formation energy for Au nanocrystals with different size supported on and embedded in SiO₂. The calculations are performed crossing our previous data on the surface free energy of the supported and embedded nanocrystals with the theoretical surface-area-difference model developed by W. H. Qi for the description of the size-dependent thermodynamics properties of low-dimensional solid-state systems. Such calculations are employed as a function of the nanocrystals size and surface energy. For nanocrystals supported on SiO₂, as results of the calculations, we obtain, for a fixed nanocrystal size, an almost constant cohesive energy, melting temperature and vacancy formation energy as a function of their surface energy; instead, for those embedded in SiO₂, they decreases when the nanocrystal surface free energy increases. Furthermore, the cohesive energy, melting temperature and vacancy formation energy increase when the nanocrystal size increases: for the nanocrystals on SiO₂, they tend to the values of the bulk Au; for the nanocrystals in SiO₂ in correspondence to sufficiently small values of their surface energy, they are greater than the bulk values. In the case of the melting temperature, this phenomenon corresponds to the experimentally well-known superheating process.</p>