Tribological Design by Molecular Dynamics Simulation: Influence of the Molecular Structure on Wall Slip and Bulk Shear

The tribological properties of a complex branched‐hydrocarbon oil under shear in a gap between smooth iron atom surfaces were studied by large‐scale molecular dynamics (MD) simulation. The liquid was a nonpolar lubricant, i.e. a polyalphaolefin (PAO) oil mixture of 1‐decane dimer, trimer, and tetramer molecules. The rheological characteristics of the lubricant, including the shear stress and viscosity as well as the relaxation time of the liquid molecule, were calculated. The results show that, as the number of branches of the liquid molecule increases, the shear stresses and the wall slip increase. However, for a mixture fluid containing three different branched molecules, the wall slip decreases in comparison to a liquid consisting of only one kind of branched molecule.