Premium
Collisions of ideal gas molecules with a rough/fractal surface. A computational study
Author(s) -
Panczyk Tomasz
Publication year - 2007
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20472
Subject(s) - fractal dimension , fractal , surface (topology) , surface roughness , ideal gas , surface finish , asperity (geotechnical engineering) , measure (data warehouse) , argon , statistical physics , materials science , geometry , physics , mathematics , mathematical analysis , thermodynamics , atomic physics , database , computer science , composite material
The frequency of collisions of ideal gas molecules (argon) with a rough surface has been studied. The rough/fractal surface was created using random deposition technique. By applying various depositions, the roughness of the surface was controlled and, as a measure of the irregularity, the fractal dimensions of the surfaces were determined. The surfaces were next immersed in argon (under pressures 2 × 10 3 to 2 × 10 5 Pa) and the numbers of collisions with these surfaces were counted. The calculations were carried out using a simplified molecular dynamics simulation technique (only hard core repulsions were assumed). As a result, it was stated that the frequency of collisions is a linear function of pressure for all fractal dimensions studied ( D = 2, …, 2.5). The frequency per unit pressure is quite complex function of the fractal dimension; however, the changes of that frequency with the fractal dimension are not strong. It was found that the frequency of collisions is controlled by the number of weakly folded sites on the surfaces and there is some mapping between the shape of adsorption energy distribution functions and this number of weakly folded sites. The results for the rough/fractal surfaces were compared with the prediction given by the Langmuir‐Hertz equation (valid for smooth surface), generally the departure from the Langmuir‐Hertz equation is not higher than 48% for the studied systems (i.e. for the surfaces created using the random deposition technique). © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 681–688, 2007