Applications for two aspects of molecular simulations: static and dynamic

Zhang, Ruqin
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Mechanical Engineering
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This study consists of two applications of molecular simulation. For the first work, molecular simulations for self-assembled monolayer (SAM) formation on Au (111) substrate are conducted. The molecular system includes various interactions: Lennard-Jones, Morse potential, covalent bonding and metallic bonding. A multiscale frame work is developed to predict the phases of SAM formation under different coverage densities, as well as the surface stress development during the formation process. In order to investigate the surface stress generation, an adatom dipole based elastic interaction model is also employed. The ultimate simulation results for surface stress development obtained are of the same magnitude as reported in experimental observations. In the second work, the material detachment mechanism associated with chemical mechanical polishing (CMP) process is investigated. Based on an existing scratch intersection model, this work includes two parts: first, an analytical model is utilized to calculate the characteristic length that is related to the horizontal shear failure in scratch intersection model; then, molecular dynamics simulations are performed for the scratch intersection to find the associated characteristic length in atomistic scale. Both models are utilized to predict the relation between characteristic lengths and scratch depths for various values. Predictions from two approaches are compared with experimental observations to draw the correlation between experimental observations and simulation results.

Mechanical engineering