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Ligand-decorated metal surfaces play a pivotal role in various areas of chemistry, particularly in selective catalysis. Molecular dynamics simulations at the molecular mechanics level of theory are best adapted to gain complementary insights to experiments regarding the structure and dynamics of such organic films. However, standard force fields tend to capture only weak physisorption interactions. This is inadequate for ligands that are strongly adsorbed such as carboxylates on metal surfaces. To address this limitation, we employ the Gaussian Lennard-Jones (GLJ) potential, which incorporates an attractive Gaussian potential between the surface and ligand atoms. Here, we develop this approach for the interaction between cobalt surfaces and carboxylate ligands. The accuracy of the GLJ approach is validated through the analysis of the interaction of oxygen with two distinct cobalt surfaces. The accuracy of this method reaches a root mean square deviation (RMSD) of about 3 kcal/mol across all probed configurations, which corresponds to a percentage error of roughly 4%. Application of the GLJ force field to the dynamics of the organic layer on these surfaces reveals how the ligand concentration influences the film order, and highlights differing mobility in the x and y directions, attributable to surface corrugation on Co(11 2 ̄ 0). GLJ is versatile, suitable for a broad range of metal/ligand systems, and can, subsequently, be utilized to study the organic film on the adsorption/desorption of reactants and products during a catalytic process. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have a wide range of applications in nanotechnology engineering. This research aims to quantify the effect of wall vibration on n-decane molecules' diffusion in double-walled CNTs (DWNTs) with different diameters and determine the diffusion mechanisms behind it. Molecular dynamics simulations are performed to generate mass density profiles of confined n-decane molecules. The root mean square fluctuation and mean squared displacement analyses show that the confinement suppresses n-decane molecules' fluctuations. A self-diffusion coefficient of n-decane molecules in a 13.6 Å-diameter DWNT is the largest. However, the vibration enhancement of the n-decane molecules' diffusion in a 27.1 Å-diameter DWNT is 207%, more extensive than that in 13.6 Å-diameter and 10.8 Å-diameter DWNTs. The n-decane–CNT attractive interactions, extreme confinement, and surface friction affect the n-decane molecules' diffusion in CNTs with vibration. [ABSTRACT FROM AUTHOR]

A molecular dynamics simulation of the mechanisms responsible for the atomic migration and neck growth during the sintering process remains significant due to the nanoparticle size and the vacancy defect in the Fe structure. In this work, we have designed five sets of single Fe nanoparticles with different vacancy concentrations (0%, 2.5%, 5%, 7.5%, and 10%), which were used to investigate the melting and sintering processes. The existence of the vacancy introduced a vacancy proliferation mechanism, which later reduced the bonding energy of the surface atoms and made the surface diffusion easier. As a result, the melting and sintering temperatures slightly reduce according to the vacancy concentration. Atomic vector diagrams and root mean square displacement have been employed to describe the law of atomic motion; common neighbor analysis and coordination analysis have been used to investigate the structural changes within nanoparticles. The consistent results reveal the influence of vacancy defects on the melting and sintering of nanoparticles and provide a new method to reasonably control the sintering process. [ABSTRACT FROM AUTHOR]