Effect of Adhesive Interactions on Static Friction at the Atomic Scale

First-principles molecular dynamics (FPMD) simulations were used to study static friction, Fs, using model systems based on bulk and hydroxylated forms of Al2O3. The results demonstrate that Fs is significantly affected by adhesive interactions and by changes in the numbers of those interactions through the formation and dissociation of bonds across the slip interface. A model that directly incorporates the strengths of the adhesive interactions during slip is introduced to account for the effects on Fs and is found to perform satisfactorily. A procedure is developed to evaluate the strengths of these interactions using first-principles calculations. As a whole, the work clarifies how adhesive interactions affect Fs, provides a means of reducing the number of fit parameters used in modeling friction, and illustrates the importance of accounting for changes in bonding during simulations of friction.