STOCHASTIC DYNAMICS OF A SUBSYSTEM INTERACTING WITH A SOLID BODY WITHAPPLICATION TO DIFFUSIVE PROCESSES IN SOLIDS

In this paper the dynamics of a mechanical subsystem interacting with a solid body is studied. The Newton equations are transformed to a set of stochastic generalized Langevin equations describing the evolution of the coordinates of the subsystem particles. The solid is modeled a s a bath of interacting harmonic oscillators, and the effect of their spatial correlations on the statistical properties of the Langevin for ces is accounted for. The most important result is the relation establ ished between the static interaction of the subsystem with the solid b ody and the dissipative and fluctuation forces. In the particular case of a subsystem consisting of a single particle, an expression is deri ved for the friction tenser in terms of the static interaction potenti al and Debye cutoff frequency of the solid. The analysis is applied in the latter case to some simple processes occurring in solids, such as adsorption, desorption, and diffusion.