Stability of -alkanes and -perfluoroalkanes against horizontal displacement on a graphite surface.

The stability of adsorbed molecules on surfaces is fundamental and important for various applications, such as coating, lubrication, friction, and self-assembled structure formation. In this study, we investigated the structures and interaction energies () of propane, -pentane, -heptane, perfluoropropane, -perfluoropentane, and -perfluoroheptane adsorbed on the surface of CH (a model surface of graphite). The changes in (Δ = - (0)) associated with the horizontal displacement from the stable position were calculated using dispersion-corrected density functional theory (DFT; B3LYP-D3), where (0) is the at the stable position. The maximum value of Δ (Δ) associated with the horizontal displacement increased as the chain length increased. The Δ for the three -alkanes were 1.10, 1.82, and 2.35 kcal mol, respectively. The values for -perfluoroalkanes were 0.57, 0.83, and 1.04 kcal mol, respectively. The Δ values for the -alkanes were significantly larger than those for the corresponding -perfluoroalkanes. The value per carbon atom of the -alkanes ( 0.30 kcal mol) is approximately 2.5 times as large as that of -perfluoroalkanes ( 0.12 kcal mol). The Δ associated with the horizontal displacement of propane and perfluoropropane on circumcoronene (CH) obtained by the B3LYP-D3 calculations are close to those obtained by the second order Møller-Plesset (MP2) and dispersion-corrected double hybrid DFT calculations, suggesting the sufficient accuracy of the Δ obtained by the B3LYP-D3. Thus, our quantitative analysis revealed the higher stability of -alkanes against horizontal displacement on a graphite surface than that of -perfluoroalkanes.