Bases of chemical force microscopy by friction: Energetics and dynamics ofwearless friction between organic monolayers in terms of chemical and physical properties of molecules

Molecular dynamics and simple phenomenological simulations are used to mode l the friction between two ordered monolayers of alkyl chains bound at thei r ends, i.e.,pinned atoms, to rigid substrates. We could previously interpr et the origin of friction differences in organic monolayer systems by compa ring these two simulations. In the present work, insight given by such comp arisons is described in detail. In particular, the molecular mechanism of e nergy dissipation, the origin of friction force microscopic image, the chai n length dependence, the packing density (tilt angle) dependence, and aniso tropy of friction due to sliding direction are discussed by taking into acc ount the effects of the molecular properties on two simplified potentials o f the, monolayer films. One potential is due to the lateral collective defo rmation of a film, and the other is a corrugated interfacial potential betw een films facing each other. This interpretation of molecular lubrication m echanisms in terms of the chemical and physical properties of molecules usi ng the simple phenomenological model. Can be extended widely to understand the bases of chemical force microscopy by friction force microscopy.