Analysis of the Nucleation of Silver on Sodium Chloride

Abstract

The data of Walton, Rhodin, and Rollins for the nucleation rate of silver on sodium chloride is analyzed using classical nucleation theory. The difference between the activation energies for desorption and surface diffusion, ΔG_des—ΔG_sd, is found to be 0.3 eV, essentially independent of the value used for γ, the surface free energy of silver. The product γ³f(θ), where f(θ) is the contact angle function, is found to be 1.24×10⁹ erg³/cm⁶. With γ=1140 erg/cm², f(θ) is 0.839 and the contact angle, θ, is 119 deg. Using values of 1100 to 1600 erg/cm² for γ results in contact angles of 133 to 75 deg. Since a Pound plot of the data produces a straight line, it is concluded that Walton's data may be interpreted by the formalism of classical nucleation theory. The radius of the critical sized nucleus, r^*, is 2 to 3 Å, typical of other nucleation data analyzed in this manner.