Adsorption-induced surface normal relaxation of a solid adsorbent

Usenko Usenko

doi:10.5488/cmp.19.33603

Abstract

We investigate adsorption of a gas on the flat surface of a solid deformable adsorbent taking into account thermal fluctuations and analyze in detail the effect of thermal fluctuations on the adsorbent deformation in adsorption. The condition for coexistence of two states of a bistable system of adsorbed particles is derived. We establish the specific properties of the adsorption-induced surface normal relaxation of an adsorbent caused by thermal fluctuations. The mean transition times between two stable states of the bistable system are derived in the parabolic approximation and in the general case.

Highlights

Investigation of adsorption of gas particles on the surfaces of solids is very important for solving various problems of physics and chemistry
It should be noted that the hysteresis of adsorption isotherms due to retardation effects in the case where the typical adsorption–desorption time is much less than the relaxation time of the adsorbent surface was predicted by Zeldovich [28] as early as in 1938
The Maxwell concentration (21) agrees with the corresponding expression for the phase transition pressure for the classical Fowler-Guggenheim adsorption isotherms in the case of attractive lateral interactions of adparticles on a nondeformable adsorbent [17] if the maximum increment of the activation energy for desorption of adparticles |V a| caused by the adsorbent deformation in (8) is replaced by the modulus of the energy of attractive lateral interaction of two neighboring adparticles for θ = 1 multiplied by the coordination number of the lattice of adsorption sites

Summary

Introduction

Investigation of adsorption of gas particles on the surfaces of solids is very important for solving various problems of physics and chemistry. One of the ways of correct description of these transitions is taking account of fluctuations in a system This problem is closely connected with investigation of the effect of fluctuations on the normal displacement of the adsorbent surface caused by. We generalize the model of adsorption of a gas on the flat surface of a deformable solid adsorbent proposed in [27] for the case taking into account thermal fluctuations in the system. The corresponding times are obtained in Appendix

Statement of the problem and general relations

Probability density

Conclusions