Realistic interatomic potential for MD simulations

The coefficients of interatomic potential of simple form Exp-6 for neon are obtained. Repulsive part is calculated ab-initio in the Hartree-Fock approximation using the basis of atomic orbitals orthogonalized exactly on different lattice sites. Attractive part is determined empirically using single fitting parameter. The potential obtained describes well the equation of state and elastic moduli of neon crystal in a wide range of interatomic distances and it is appropriate for molecular dynamic simulations of high- temperature properties and phenomena in crystals and liquids

Thermodynamics and kinetics of boundary friction

A deterministic theory describing the behavior of an ultrathin lubricant film between two atomically-smooth solid surfaces is proposed. For the description of lubricant state the parameter of excess volume arising due to chaotization of solid medium structure in the course of melting is introduced. Thermodynamic and shear melting is described consistently. Dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces are analyzed. Within the framework of a simple tribological model the stick-slip mode of friction, when the lubricant periodically melts and solidifies, is described. The obtained results are qualitatively compared with the experimental data.Comment: 14 pages, 6 figures, 33 reference

Thermodynamics and kinetics of boundary friction

A deterministic theory describing the behavior of an ultrathin lubricant film between two atomically-smooth solid surfaces is proposed. For the description of lubricant state the parameter of excess volume arising due to chaotization of solid medium structure in the course of melting is introduced. Thermodynamic and shear melting are described. Dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces are analyzed. Within the framework of a simple tribological model the stick-slip mode of friction, when the lubricant periodically melts and solidifies, is described. The obtained results are qualitatively compared with the experimental data. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1808

Phenomenological Theory for the Melting of a Thin Lubricant Film between Two Atomically Smooth Solid Surfaces

A thermodynamic model is developed for the melting of an ultrathin lubricant film squeezed between two atomically smooth solid surfaces. To describe the state of lubricant, an excess volume parameter is introduced; it appears due to the chaos in the structure of a solid body induced by melting. This parameter increases with the total internal energy upon melting. Thermodynamic melting and shear melting are described. The dependences of the friction force on the lubricant temperature and the shear rate of friction surfaces are analyzed. The calculated results are compared to the experimental data. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1809

Multidimensional thermodynamic potential for descriptions of ultrathin lubricant film melting between two atomically smooth surfaces

The thermodynamic model of ultrathin lubricant film melting, confined between two atomically-flat solid surfaces, is built using the Landau phase transition approach. Non-equilibrium entropy is introduced describing the part of thermal motion conditioned by non-equilibrium and non-homogeneous character of the thermal distribution. The equilibrium entropy changes during the time of transition of non-equilibrium entropy to the equilibrium subsystem. To describe the condition of melting, the variable of the excess volume (disorder parameter) is introduced which arises due to chaotization of a solid structure in the course of melting. The thermodynamic and shear melting is described consistently. The stick-slip mode of melting, which is observed in experiments, are described. It is shown that with growth of shear velocity, the frequency of stiction spikes in the irregular mode increases at first, then it decreases, and the sliding mode comes further characterized by the constant value of friction force. Comparison of the obtained results with experimental data is carried out.Comment: 11 pages, 4 figure

Nonlinear thermodynamic model of boundary friction

Melting of an ultrathin lubricant film confined between two atomically flat surfaces is studied. An excess volume parameter is introduced, the value of which is related to the presence of defects and inhomo-geneities in the lubricant. Via minimization of the free energy, the Landau—Khalatnikov kinetic equation is obtained for this parameter. The kinetic equation is also used for relaxation of elastic strains, which in its explicit form contains the relative shear velocity of the rubbing surfaces. With the numerical solution of these equations, a phase diagram with domains corresponding to the sliding and dry stationary friction regimes is built at a fixed shear velocity. A simple tribological system is used to demonstrate that in the dynamic case, three friction regimes can occur, namely, dry, stick-slip, and sliding friction. It is shown that a lubricant can melt when the shear velocity exceeds a critical value and with elevation of its temperature. The dependence of the dynamic friction force on the pressure applied to the surfaces, the temperature of the lubricant, and the shear velocity is considered. It is shown that growth of pressure leads to the forced ordering and solidification of the lubricant. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1809

Неравновесная эволюционная термодинамика граничного трения

Запропоновано загальну термодинамічну модель плавлення ультратонкої плівки мастила. Знайдено значення критичної швидкості зсуву, при якому мастило плавиться за механізмом зсувного плавлення. Показано, що при температурі поверхонь тертя вище за критичне значення воно плавиться навіть при нульовій швидкості зсуву, оскільки відбувається повне термодинамічне плавлення. Знайдені особливості якісно збігаються з експериментальними даними. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/3556The general thermodynamic model of ultrathin lubricant film melting is proposed. The critical value of shear velocity, at which lubricant melts according to the shear melting mechanism, was found. It was shown that at temperature of rubbing surfaces above the critical value it melts even at zero shear velocity since total thermodynamic melting is realized. Found features coincide qualitatively with experimental data. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/355