Adsorption enhancement of a fatty acid on iron surface with Σ3(1 1 1) grain boundary

Abstract

Nanocrystallization processes applied to metallic surfaces can enhance their tribological properties under boundary lubrication. To reveal the mechanism, the adsorbability of acetic acid as a fatty lubricant molecule on a nanostructured iron surface was investigated using first-principles calculations. The nanostructured surface was modeled as a surface slab including a grain boundary (GB) per unit cell. Comparing the adsorbability of the Fe (110) surface with symmetrical tilt Σ3 (111) grain boundaries to that of an Fe (110) surface without GBs, we found that the molecule tends to be adsorbed more strongly (0.76 eV in average) on sites close to the grain boundary than on the clean surface. A local energy analysis revealed that the adsorption was enhanced even at a relatively distant position (approximately 5 Å from the adsorbed molecule) and that the energy contributions of atoms of different types were qualitatively different for the adsorption on the surface with GBs.