Molecular dynamics simulations are used to study CO adsorption on Ag nanoclusters ranging from 38 to 500 Ag atoms, supported on carbon nanotube. Each nanocluster was simulated under various pressures of CO gas at different temperatures. The absolute value of enthalpy of adsorption was calculated for all of the nanoclusters in constant coverage which is increased sharply by decreasing cluster size. This increasing trend with coverage reaches a maximum around 0.75 ML for Ag 108 . Also, the structural changes are irreversible in such a way that by gradually decreasing the pressure to zero, the nanocluster geometry is not reversed to its initial structure in vacuum conditions. It was found that structural irreversibility increases with the size. Also, the difference between diffusivity of Ag nanoclusters in vacuum and CO atmosphere increases with the size.

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In the present study, a computational investigation on the effect of surface roughness on the wettability behavior of water nanodroplets has been performed via molecular dynamics simulation. To fabricate the roughness, several grooves with different depths and widths were considered on the top layer(s) of graphite. Free energy analysis indicates that surface roughness reduces the solid-liquid adhesion and the work done for the removal of the nanodroplet from the solid surface. This reduction increases with an increase in both the depth and width of the grooves. Furthermore, the adhesion in Wenzel state is greater than that in the Cassie-Baxter state. Results show that increasing the depth and decreasing the width of the grooves decrease the wettability and the nanodroplet locates in the Cassie-Baxter state. In addition, both the Cassie-Baxter and Wenzel models effectively predict the nanodroplet contact angle on the rough surfaces. Furthermore, the probability of successful interactions decreases in the solid-liquid interfaces due to the heterogeneity of the surface. Therefore, the density, the residence time and the hydrogen bond lifetime of the water molecules in the layer in the vicinity of the substrate decrease. In addition, surface roughness affects the orientation of the water molecules at the interface, the diffusion of water molecules as well as the movement of the water nanodroplet.

Molecular dynamics simulations were used to investigate the adsorption effects of different gas phases on structural and dynamical properties of graphite-supported Ag nanoclusters at various pressures, temperatures, and cluster sizes. Three Ag nanoclusters with N = 38, 108, and 256 atoms in vacuum and under pressure of five gases (He, Ar, Xe, H 2 , and CO) were simulated. The effect of each gas on nanoclusters at four temperatures and at various numbers of gas atoms (various pressures) was investigated. The adsorption, structural changes, and dynamic properties were monitored as a function of cluster size, pressure, and temperature. The adsorption isotherms, density profiles, deformation parameter, mean-square displacement, and diffusivity were calculated to study structural changes and dynamical properties of nanoclusters. It was found that the adsorption isotherms comply from the Langmuir type I. Also, the gas phase changes the vacuum cluster structure irreversibly. Furthermore, the gas phase increases the diffusivity of nanoclusters on the substrate surface, and this diffusivity increases with gas pressure.

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