| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 95 === The dynamical behaviors of tricarboxylic acid derivative, 1,3,5-tris(carbox- ymethoxy) benzene[TCMB, C6H3(OCH2COOH)3] on an Au surface is investigated by molecular dynamics. A TCMB molecule adsorbed on the Au(111) substrate is first probed into the structure arrangement. It founds that there are four possible conformations of the TCMB molecule that is adsorbed on the Au(111) substrate. The main difference on its conformation is the orientation of its functional group, which lead the molecule that forms the lock-and-key (LAK) behavior and prompts the molecule that become more stable on the substrate. As this result, the LAK behavior directly affects the trajectories of movement and dynamical behaviors.
Another topic is to observe the behavior of TCMB molecule on Au(110) and Au(100) surface, respectively. As well as the result of the TCMB molecule adsorbed on the Au(111) substrate, it also shows a different behavior on dynamical behaviors when the TCMB molecule adsorbed on the Au(110) and Au(100) substrate. Moreover, we found that the diffusion direction of TCMB molecule is dependent on the arrangement of the adsorbed surface. From the observation of the trajectory of the TCMB molecule, we found that diffusion range is most wide on Au(100) plane. The translational direction of TCMB molecule tend to move on the <110> direction as the molecule is migrate on the Au(100) plane, whereas that tend to move on the [1ī0] direction as the molecule is migrate on the Au(110) plane.
From the description above, we know that TCMB molecule with different conformations on different plane of surface arrangement displays different trajectories of movement and dynamical behaviors. Therefore, in order to understand the dynamical behaviors of TCMB monolayer on gold surface. In this work, the temperature effect on the adsorption behavior and the dynamic behavior of TCMB monolayer structure on the Au(111) substrate are investigated. From the calculation of the cohesive energy between molecules and the interaction energy between the molecule and the Au(111) substrate, we found that there are significant changes in cohesive energy and interaction energy at specific temperatures, which can be attributed to the deformation of the monolayer structure. Finally, the mean square displacement (MSD), diffusion coefficient(D) and distance between the molecule and the Au(111) substrate are calculated to investigate the diffusion property and motion behavior of TCMB monolayer at specific temperatures.
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