Abstract: Pentaerythritol tetra (2-ethylhexanoate) (PETE) has been used as an environmentally friendly lubricant. Molecular dynamics (MD) simulations based on polymer consistent force field (PCFF) are adopted to investigate the molecule and density distributions of lubricant PETE in nanogap at two different temperatures, three different initial film thicknesses and a wide range of pressures. Results show that the densities of MD simulations are accurate to the values of Tait equation with the maximum initial film thickness (9.17nm), the deviations are less than 5%. The film thickness and compressibility of films decrease with increasing pressure on the wall, but the compressibility is similar for films with different initial film thicknesses. Because the PETE molecule consists of four long branched chains, different spatial scales are in the same magnitude, the phenomenon of fluid atoms tending to form layers parallel to confining walls has not been observed except for the regions of lubricant adjacent walls. Distinct excluded volumes have not been found at the liquid/wall interfaces.

Key words: compressibility, molecular dynamics simulation, pentaerythritol tetra, polymer consistent force field, thin film lubrication