| As the design of devices and applications becomes increasing complex, the interfaces of advanced materials have a pervasive influence on a variety of engineered properties. In functional ceramics, the electronic conductivity is strongly impacted by the ion arrangement at grain boundaries. Interlayer dielectric materials such as thin films with nanoscale porosity require structure with precisely controlled interfaces. In addition, the environment in which surfaces are coated is often very different from the environment they are subjected to in tribological application. To engineer materials with desired properties, it is thus important to understand these interfaces at the atomic level. In this dissertation, ab initio calculations and molecular dynamics (MD) simulations were carried out toward the understanding of different interfaces.;Defects in titanium dioxide (TiO2) grain boundaries are investigated where the bulk properties are largely determined by these internal interfaces. Defect formation energies in TiO2 grain boundaries are calculated using density functional theory (DFT) and are compared to corresponding energies in bulk TiO2. In particular, various Schottky and Frenkel defects complexes are considered.;The morphology and mechanical properties of surfactants, which are surface active agents that are used as organic templates in mesoporous silica thin films and in the synthesis of other emerging technologies, are investigated. Classical molecular dynamics simulations with empirical potentials are used to compare the structures and mechanical properties of cationic surfactant micelles that are being indented with carbon nanotubes and silica nanowires at the silica-water interface. The findings are compared to the results of bulk indentation with graphite and silica surfaces, and the influence of nanometer-scale curvature on the results is described.;A tribological study of polyethylene (PE), a widely used polymer with great wear resistance and other advantageous tribological properties, was carried out to gain insight into the atomic-level origins of friction. The role of sliding orientation, surface loading, temperature, crosslinking, and composite sliding on the tribological behavior of PE is investigated using classical molecular dynamics simulations. At various temperatures, oriented crosslinked PE surfaces are slid in different sliding directions and applied normal loads. The tribological behavior of different crosslinked PE surfaces is compared, and the differences and similarities are discussed. |
