Physical dissipation mechanisms in non-contact atomic force microscopy

Using realistic molecular dynamics simulations on the MgO(001) surface we show that the friction coefficient and dissipation energies due to the stochastic friction force mechanism are much smaller than observed experimentally in close agreement with previous analytical models. Therefore, the method is generalized by including a single soft vibrational mode at the surface. Using methods of non-equilibrium statistical mechanics, we derive an equation of motion for the tip interacting with the soft mode. It is shown that this method enables the simultaneous description of both stochastic friction and adhesion.