When an analysis of a fluid flow is performed on a macroscopic level, often two assumptions are taking place. First is an assumption of a continuously distributed matter (continuum), the second is a zero relative fluid velocity at the fluid-surface interface, often referred as no-slip condition. Both assumptions do not count in the atomic nature of a real fluid, since the flow friction is dependant on the asymmetricity of the outbound angle when an atom collision is taking place. In the ideal case, after a flow atom collided with the wall surface the inbound angle is the same as the outbound angle, because only then, no tangential force has been transferred to the wall, consequently the fluid viscosity, as a macroscopic quantity, is zero.
A two- and three-dimensional numerical simulation of the outbound angle scattering of monatomic gases (argon and krypton) on monocrystal lattices of pure metals (silver and platinum) was made. For the analysis we used a software called LAMMPS. All the calculations took place with energies where quantum nature of the materials was not significant. An outbound angle probability density distribution was made for inbound angles of 30, 45 and 60 degrees regarding the surface normal at different lattice orientations (100 and 111). We had compared our two-dimensional scattering results with the measurements in the literature, broadened them to three-dimensional scale and presented the results.
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