Abstract
A possible mechanism of atomic scale dissipation in non-contact atomic force microscopy (NC-AFM) is investigated using a non-equilibrium classical molecular dynamics simulation method with stochastic boundary conditions. We find that for simple flat crystal surfaces, such as the MgO(001) which does not possess intrinsic surface soft vibrational modes, dissipation effects can be explained by tip induced soft modes associated with well-known atomic instabilities produced by the approaching tip. Extrapolating results of calculations performed for a succession of tip oscillation frequencies, we suggest that dissipation energies can be obtained via this mechanism which are of the same order of magnitude of experimentally observed contrasts.