How to identify haeckelite structures: A theoretical study of their electronic and vibrational properties

First-principles (FP) calculations of the electronic and vibrational properties of three different Haeckelite structures have been performed. The relatively low cohesive energies (when compared to C₆₀) of these phases suggest the possible synthesis of such novel carbon arrangements. In agreement with previous tight-binding calculations (Terrones, H.; Terrones, M.; Hernandèz, E.; Grobert, N.; Charlier, J.-C.; Ajayan, P. M. Phys. Rev. Lett. 2000, 84, 1716), the Haeckelite structures exhibit a clear metallic behavior. In addition, within the ab initio framework, we predict the IR and Raman frequencies, which constitute the fingerprint of their structure and allow for their unambiguous identification. STM images and quantum conductances of various tubular Haeckelite structures are also calculated within a tight-binding framework. The three investigated Haeckelite structures are shown to be good candidates of conducting wires with great potential in nanoelectronics. The results presented here provide a catalog of properties that will aid in the identification of other Haeckelite structures as well as carbon systems containing pentagonal and heptagonal defects.