Kinetic model of adsorption on crystal surfaces

Abstract

A kinetic theory model describing physisorption and chemisorption of gas particles on a crystal surface is introduced. A single kinetic equation is used to model gas and physisorbed particles interacting with a crystal potential and colliding with phonons. The phonons are assumed to be at equilibrium and the physisorbategas equation is coupled to similar kinetic equations describing chemisorbed particles and crystal atoms on the surface. A kinetic entropy is introduced for the coupled system and the H theorem is established. Using the Chapman-Enskog method with a fluid scaling, the asymptotic structure of the adsorbate is investigated and fluid boundary conditions are derived from the kinetic model.

Kinetic theory of chemical reactions on crystal surfaces

“…A kinetic model describing multicomponent gases nearby reactive crystal surfaces is presented. The kinetic equations involve monatomic or polyatomic particles interacting with surface potential fields and colliding with phonons, [19,20,21,22,23,32,33,34]. This complex chemistry collisional formalism for surface reactions is new to the best of the authors' knowledge.…”

“…where n = n g + n c + n s + n b is the total number of reactive species at the surface. The Boltzmann equations governing physisorbed-gas species are in the form [19,20,21,22,23,32,33,34]…”

“…These models have been used to study condensation and evaporation, particle trapping, phonon drag, surface homogenization, or scattering kernels [19,20,21,22,23,24,25,26,27,28,29,30,31]. Such physical models have recently been extended to cover the situation of a single-species chemisorption [32,33]. In this work, a kinetic model for complex chemical reaction networks on crystal surfaces-also involving polyatomic species-is investigated expanding previous work [32,33] as well as preliminary results [34].…”

“…Such physical models have recently been extended to cover the situation of a single-species chemisorption [32,33]. In this work, a kinetic model for complex chemical reaction networks on crystal surfaces-also involving polyatomic species-is investigated expanding previous work [32,33] as well as preliminary results [34].…”

“…The sets F r and B r denote respectively the indices of reactants and products of the rth reaction. The chemical reactions are described by using the atom site formalism that takes into account the crystal atoms, even though macroscopically it may also be described by using the open site formalism that formally hides the crystal atoms [17,33]. The surface chemical reaction mechanism is arbitrarily complex and covers adsorption, desorption, Langmuir-Hinshelwood as well as Eley-Rideal reaction types.…”