Diameter Control of Single-Walled Metal Oxide Nanotubes Sankar Nair, School of Chemical & Biomolecular Engineering, Georgia Institute of Technology The yet-unrealized capability to engineer nanotube materials of precisely controllable diameters below 5 nm, using low-temperature aqueous phase synthesis, will allow many potential applications as catalytic, photonic, electronic, and biotechnological materials among others. One main impediment towards this goal is the lack of understanding of the energetics of nanotube materials. A recent achievement of our research is summarized in the images. Below left: Using detailed atomistic simulations and theoretical modeling, we have discovered that the diameter of single-walled metal oxide nanotubes can be varied with angstrom-level precision by making compositional variations that tune the interatomic potential energies in the material. Below right: our computational results (green line) and theoretical predictions (red line) are validated by our experimental results showing the increasing diameter of the nanotube as the silicon atoms are progressively substituted by germanium atoms.