The composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation, experimental results are first presented which demonstrate that mineral grains subjected to high temperatures in a reducing environment lead to iron nanoparticles which are strongly catalytic for the formation of complex organic species. Next, results obtained using molecular-dynamics simulations demonstrate that uncoordinated surface atoms in metallic nanoparticles result in plastic deformation, strong dissipation and adhesion during collisions. This can be contrasted with previous simulations which demonstrate significantly weaker dissipation when surface atoms are passivated. Calculations of critical sticking velocities demonstrate that simple coarse- grain models are insufficient for predicting the adhesive behavior of sub-micron sized grains. Next, results are presented describing a computational study illuminating the role of surface chemistry on adhesion and dissipation for iron nanoparticle collisions, which in the case of free radical adsorbates may also contribute to the creation of more complex species. Lastly, to further elucidate dissipation, the direct coupling of harmonic vibrational modes in the dissipation process is established. The results demonstrate broad participation of low and high-frequency modes during a collision during a timescale less than time required for particles to rebound. Hence, our results demonstrate extremely strong likelihood of adhesion during collisions. This approach provides a way to use density-functional theory calculations to directly compute dissipative couplings at mineral interfaces.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Tucker, William, "Chemistry and Dissipation at Mineral Surfaces in the Space Environment" (2019). Electronic Theses and Dissertations. 6345.
Restricted to the UCF community until May 2019; it will then be open access.