Electronic and structural properties of carbon nanohorns

We use a parametrized linear combination of atomic orbitals calculations to determine the stability, optimum geometry, and electronic properties of nanometer-sized capped graphitic cones, called ‘‘nanohorns.’’ Different nanohorn morphologies are considered, which differ in the relative location of the five terminating pentagons. Simulated scanning tunneling microscopy images of the various structures at different bias voltages reflect a net electron transfer towards the pentagon vertex sites. We find that the density of states at the tip, observable by scanning tunneling spectroscopy, can be used to discriminate between different tip structures.