Abstract
The interaction of molecules and atoms with the surface of a solid is considered on the basis of classical mechanics. A two-dimensional square lattice with atoms arranged at the lattice points was taken as the model for describing a solid. It is assumed that only neighboring atoms interact in the solid, while the gas molecules interact with the atoms located in its surface layer.
As a result of “collisions” with the surface, a gas molecule loses a part of its kinetic energy, and this process is characterized by the energy accommodation coefficient. In addition, another coefficient is introduced which takes account of that part of the energy of translational motion converted into energy of internal motion of the molecule (vibration and rotation). The possibility of the occurrence of inelastic losses and some special features of this phenomenon are illustrated by the interaction of a diatomic molecule with an isolated atom.
The available experimental data on the interaction of particles of gas with the surface of a solid are essentially associated with the low-energy region (the temperature of the gas is less than or on the order of several hundreds of degrees). One of the objectives of this research was to find the distribution function of particles reflected from the surface; in particular, the hypothesis of diffuse-specular reflection is tested [1–3]. However, the few experimental results provide evidence of the effect of a large number of factors on the nature of the interaction, rather than make it possible to establish strict laws for the process.
The theoretical investigations were conducted along the line of improving simple models-instead of modelling a solid by a one-dimensional chain of atoms [4,5], two and three-dimensional lattices are introduced [6–8]. It is noted in [6] that the interaction of gas particles with a one -dimensional chain differs from the interaction with a three-dimensional lattice, and this fact can lead to a considerable divergence in the values of the accommodation coefficient when the mass of the incident molecule is comparable with the mass of an atom of the solid. It also follows from [6] that if we describe the interaction between gas atoms and those of the solid by the Morse potential, then we can select the parameters of the potential so that the calculated data will agree with the experimental data. Moreover, good results are obtained if we make use of parameters of the potential determined on the basis of the combination rule [7].
The interaction of atoms of gas with a three-dimensional lattice of finite size is considered in [8]. Forces with the Lennard-Jones potential act between gas atoms and atoms of the solid. The classical equations of motion of all particles were solved numerically on electronic computers.
In these references, a gas particle (molecule or atom) is regarded as a whole; however, the problem of the influence of internal degrees of freedom on the coefficients of energy and momentum exchange between the gas particles and the solid is interesting. An attempt is made in this work to take this influence into account on the basis of classical mechanics.
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Erofeev, A.I. Interaction of molecules with the surface of a solid. J Appl Mech Tech Phys 7, 26–30 (1966). https://doi.org/10.1007/BF00914693
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DOI: https://doi.org/10.1007/BF00914693