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Journal of Materials
Volume 2015, Article ID 963257, 13 pages
http://dx.doi.org/10.1155/2015/963257
Research Article

Molecular Dynamics Study on Lubrication Mechanism in Crystalline Structure between Copper and Sulfur

1Department of Mechanical Engineering, Faculty of Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan
2Kobe Steel Ltd., 2-3-1 Shinhama, Arai-cho, Takasago, Hyogo 676-8670, Japan

Received 11 August 2015; Revised 24 September 2015; Accepted 29 September 2015

Academic Editor: Te-Hua Fang

Copyright © 2015 Ken-ichi Saitoh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

To clarify the nanosized mechanism of good lubrication in copper disulfide (Cu2S) crystal which is used as a sliding material, atomistic modeling of Cu2S is conducted and molecular dynamics (MD) simulations are performed in this paper. The interatomic interaction between atoms and crystalline structure in the phase of hexagonal crystal of Cu2S are carefully estimated by first-principle calculations. Then, approximating these interactions, we originally construct a conventional interatomic potential function of Cu2S crystal in its hexagonal phase. By using this potential function, we perform MD simulation of Cu2S crystal which is subjected to shear loading parallel to the basal plane. We compare results obtained by different conditions of sliding directions. Unlike ordinary hexagonal metallic crystals, it is found that the easy-glide direction does not always show small shear stress for Cu2S crystal. Besides, it is found that shearing velocity affects largely the magnitude of averaged shear stress. Generally speaking, higher velocity results in higher resistance against shear deformation. As a result, it is understood that Cu2S crystal exhibits somewhat liquid-like (amorphous) behavior in sliding condition and shear resistance increases with increase of sliding speed.