Extended Huckel theory for bandstructure, chemistry and transport. I. Carbon Nanotubes

We describe a semi-empirical atomic basis Extended H\"uckel Theoretical (EHT) technique that can be used to calculate bulk bandstructure, surface density of states, electronic transmission and interfacial chemistry of various materials within the same computational platform. We apply this method to study multiple technologically important systems, starting with carbon-nanotubes (CNT) and their interfaces in this paper, and silicon-based heterostructures in our follow-up paper. We find that when it comes to quantum transport through interesting, complex heterostructures, the Huckel bandstructure offers a fair and practical compromise between orthogonal tight-binding theories (OTB) with limited transferability between environments under large distortion, and density functional theories (DFT) that are computationally quite expensive for the same purpose.