Revisiting Scattering Dynamics of Gaseous Ne Atoms off the Squalane Liquid Surface with Fine-Tuned All-Atom Force Field and GPU

We conducted GPU-accelerated molecular dynamics (MD) simulations to revisit the scattering dynamics of neon (Ne) atoms off the squalane liquid surface, using a fine-tuned all-atom general AMBER force field (ft-GAFF) with more than 10,000 trajectories per initial condition. The fine-tuned force field generated a molecular structure that exhibited more efficient energy transfer and reproduced the experimental density more accurately than the united-atom TraPPE-UA (Transferable Potentials for Phase Equilibria-United Atom) force field used by [Peng, Y. J. Phys. Chem. C 2008, 112(51), 20340–20346]. The residence time of Ne ranged from 5 to 11 ps, with the number of kicks typically ranging from 3 to 8. Bimodal energy distributions corresponding to thermal-desorption (TD) and impulsive scattering (IS) mechanisms were identified. Unlike previous simulation, the present work presents more details of simulations and integrates recent findings to further analyze the scattering system. We confirmed that, under different incident conditions, the IS fraction is always higher than the TD fraction. The low incident energy and small incident angle are favorable for TD, and the angular distribution of TD fractions follows a cosine distribution similar to evaporation. In contrast, IS prefers high incident energy and large incident angle and tends to near-specular scattering. Meanwhile, the IS channel was analyzed to explore energy transfer between Ne and squalane as a function of the deflection angle. Comparisons with the Ne-dodecane system further highlighted the role of surface structure in scattering dynamics.