Freezing and Melting of Silver Nanoparticles on Silica Substrate Using a Simple Interatomic Potential for Ag–SiO 2 Interaction on the Basis of ab Initio Calculations and Experimental Data

We have devised a Ag−SiO 2 potential for Monte Carlo and molecular dynamics studies of systems comprising silver nanoparticles in contact with silica surfaces. The potential is determined based on density functional theory (DFT) calculations on β-cristobalite, a silica crystal, as well as theoretical and experimental data on α-quartz and amorphous silica found in literature. The interactions between Ag and silica species are fitted with the simple Lennard-Jones (12, 6) potential with parameters σ Ag−O = 0.278 nm, σ Ag−Si = 0.329 nm, ε Ag−O = 0.012 eV, and ε Ag−Si = 0.002 eV. The nature of the substrate is taken into account at a phenomenological level as an extra multiplicative factor η for the total interaction between silver and silica: for α-quartz η quartz = 1, for hydroxylated β-cristobalite η crist = 5.0, and for amorphous silica η amorph = 2.5. This potential is thought to be useful to investigate the effect of the silica support on the structure and morphology of deposited silver nanoparticles. As an example, we study the melting and freezing of supported nanoparticles. This potential could also possibly be extended to other metals or support.