Band structures built by the elongation method

摘要

A recently proposed approach for extracting band structures from finite-cluster calculations isimproved so that (avoided) band crossings can be handled and the problems related to so-calleddoublings and holes are reduced. In particular, we demonstrate how the method can be combinedwith the elongation method for the finite-system calculations and apply it to extracting bandstructures for polymers from oligomer calculations. As illustrations of the approach we discuss achain of water molecules, polyacetylene, polyethylene, and a BN nanotube without and with animpurity.