Physics Commons^™

Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha

Doctoral Dissertations

The narrow hydrophobic interior of a carbon nanotube (CNT) poses a barrier to the transport of water and ions, and yet, unexpectedly, numerous experimental and simulation studies have confirmed fast water transport rates comparable to those seen in biological aquaporin channels. These outstanding features of high water permeability and high solute rejection of even dissolved ions that would typically require a lot of energy for separation in commercial processes makes carbon nanotubes an exciting candidate for desalination membranes. Extending ion exclusion beyond simple mechanical sieving by the inclusion of electrostatics via added functionality to the nanotube bears promise to not …

First-Principles Study Of Point Defect Behavior At Interfaces And In-Plane Strain Fields, Jianqi Xi

Doctoral Dissertations

Interfaces in solid materials are the so-called boundaries, separating crystals with the same structure and chemistry but different orientations, e.g. grain boundaries (GBs), different stacking sequences, e.g. stacking faults (SFs), or crystals with different structures and/or chemistries as well as orientations, e.g. the interface between substrate and thin film. In this study, first-principles calculations are used to investigate the defect behavior at different interfaces and in-plane strain fields, such as stacking fault (SF) in silicon carbide (SiC), in-plane strain field near interfaces in potassium tantalate (KTaO₃), and grain boundary in ceria (CeO₂).

Results show that the …

Surface Energy In Bond-Counting Models On Bravais And Non-Bravais Lattices, Tim Ryan Krumwiede

Doctoral Dissertations

Continuum models in computational material science require the choice of a surface energy function, based on properties of the material of interest. This work shows how to use atomistic bond-counting models and crystal geometry to inform this choice. We will examine some of the difficulties that arise in the comparison between these models due to differing types of truncation. New crystal geometry methods are required when considering materials with non-Bravais lattice structure, resulting in a multi-valued surface energy. These methods will then be presented in the context of the two-dimensional material graphene in a way that correctly predicts its equilibrium …