Nanoscale physics

Molecular dynamics of shear of ultrathin film of carbon disulfide between diamond surfaces
Khomenko A.V., Boyko D.V., Goncharenko N.G.
Sumy State University, 2, Rimsky Korsakov Str., 40007 Sumy, Ukraine. 
E-mail: o.khomenko@mss.sumdu.edu.ua

The development of wear-resistant surfaces with low friction and thin lubricant films has become an important factor in the miniaturization of moving parts in many technical devices, e. g. microelectromechanical systems, computer storage systems, miniature engines and so on. The calculations were carried out for plane Couette flow geometry [1], which resembles the experimental systems investigated by the surface forces apparatus. An ultrathin film of carbon disulfide was considered, bounded by two solid diamond walls with periodic boundary conditions in the plane of the plates applied to both the liquid and the surfaces. Atomically-smooth and periodic relief plates were studied. To simplify the task, the plates are considered to be absolutely rigid, and the model does not include the elasticity of the surfaces. The behavior of the friction force, kinetic and total energies is simulated. It can be concluded that the linear increase in the friction force with the load is determined not by the relief of the surfaces, but by their elasticity. The rapid saturation of the friction force is observed with a growth of the load for all the models considered. Fluctuations of kinetic energy significantly increase the amplitude during the loading on the surface, this indicates an ascent of the temperature of the liquid molecules. Generally, the time dependences of the friction force reflect solid-like structure of film. Increase of external load leads to a gradual transition of a film to the solid-like state. The dependences of friction force on time, external load (surface pressure), and shear force are investigated showing different rubbing modes. The dependences of shear stresses on the load show similarities with the experimental dependences for simple spherical molecules.

1.	Khomenko A.V., Boyko D.V., Zakharov M.V., Molecular dynamics of a thin liquid argon layer squeezed between diamond surfaces with a periodic relief // J. Frict. Wear.-2018.-39, No. 2.-P. 152-157.