Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2012 - 20162

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Subject: search.filters.subject.Molecular Dynamics Simulation

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    Wetting of Graphene
    (2016) Andrews, Joseph E.; Das, Siddhartha; Chung, Peter W.; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Graphene, a remarkable 2D material, has attracted immense attention for its unique physical properties that make it ideal for a myriad of applications from electronics to biology. Fundamental to many such applications is the interaction of graphene with water, necessitating an understanding of wetting of graphene. Here, molecular dynamics simulations have been employed to understand two fundamental issues of water drop wetting on graphene: (a) the dynamics of graphene wetting and (b) wetting of graphene nanostructures. The first problem unravels that the wetting dynamics of nanodrops on graphene are exactly the same as on standard, non-2D (or non-layered) solids – this is an extremely important finding given the significant difference in the wetting statics of graphene with respect to standard solids stemming from graphene’s wetting translucency effect. This same effect, as shown in the second problem, interplays with roughness introduced by nanostructures to trigger graphene superhydrophobicity following a hitherto unknown route.
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    Simulations of nonuniform fluids with long-ranged and short-ranged interactions
    (2012) Liu, Shule; Weeks, John D; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The study of nonuniform fluids is of great importance in many areas of chemistry, biophysics,and materials science. Computer simulations of model systems have provided great insight into fundamental physical issues. We have studied two model systems: amphiphiles on a hydrophilic silica surface and charge overcompensation at the boundary of a colloid by multivalent ions. In the first model system, the organization of propionitrile and methanol near the surface has been studied via simulations. Both molecules can form highly organized bilayer-like structure near the surface. For propionitrile molecules, inside the bilayer-like structure hydrocarbon molecules intertwine with each other and form a closely packed structure. For methanol, molecules are strongly bonded to the silica surface with hydrogen bonds, resulting in much stronger hydrogen bonding than in the bulk and extremely slow dynamics. In our second model system, we use the local molecular field (LMF) theory to calculate the structure and solvation free energy of the system with a highly charged colloid immersed in trivalent salt. A mimic system with only short-ranged interactions was constructed using the LMF theory. By solving the LMF equation self-consistently, we have obtained the correct structure that indicates overcharging, where the charge of the colloid is overcompensated by the charge of trivalent ions. Then by taking a series of steps in a thermodynamic cycle, we have also calculated the solvation free energy of the colloid, using only results from the mimic system, and found very good agreement with more costly calculations carried out in the full long-ranged system.