The adsorption of cyclopentane and cyclohexane on the surface of magnesium oxide (100), , hexagonal boron nitride and the graphite nanoparticles were studied to investigate the role of molecular versus surface symmetry on their combined physicochemical properties. The planar D<sub>6h</sub> structure of cyclohexane (saddle point in potential energy surface) has common symmetry element(s) with all three surfaces under investigation while the planner D<sub>5h</sub> structure of cyclopentane suffers from a frustration during the adsorption process due to the lack of symmetry match with the substrates. The effect of this symmetry mismatch is clearly reflected in the layering behavior on the surfaces as established by a series of high-resolution volumetric adsorption isotherms recorded over the temperature range of 195-265K on each of the substrates. Thermodynamic properties such as the heat of adsorption, differential enthalpy, and differential entropy of adsorption during the layer growth process were calculated from the adsorption isotherm. The behavior of the two dimensional isothermal compressibility as a function of temperature and coverage was used to identify the locations of layering and potential phase transitions. To gain additional insight into the structure and dynamics of the adsorbed layers, classical molecular dynamics simulations were performed using a centralized force field (COMPASS). Molecular trajectories generated over a broad range of temperatures were analyzed to obtain binding energy and concentration profile of molecules from the surfaces. By examining the radial distribution functions the effect of surface corrugation on the structure of adsorbed layers was investigated. The results of these modeling studies will be used to aid future quasi- and inelastic neutron scattering experiments aimed at exploring the effects of surface adsorption on the rotational and translational diffusion and vibrational motion of the single and multilayer molecular films.

Comparative thermodynamic and modeling study of the adsorption of cyclopentane and cyclohexane on MgO(100), hBN and graphite basal plane

254th National Meeting (2017)

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