Conformational Effects on Structure, Electron States, and Raman Scattering Properties of Linear Carbon Chains Terminated by Graphene-Like Pieces

Carbon nanowires made of long linear atomic chains have attracted considerable interest due to their potential applications in nanoelectronics. We report a theoretical characterization of assemblies with good prospects for chemical synthesis made of two coronene molecules (graphene-like pieces) bridged by carbon linear chains with distinct sizes and parities. Our calculations are performed within all-electron density functional theory. We examine the effects of two conformations (syn and anti) of the terminal anchor pieces, representing energy minima for these systems, on the properties of the carbon chains. The calculated electronic states reveal that simplified chemical models such as those based on cumulenes or polyynes are not appropriate to describe the linear chains with sp(2) terminations. For these types of atomic chains, we find that the electronic ground state of the odd-numbered chains is spin polarized. Vibrational properties of all these chains are studied by calculating Raman scattering and infrared spectra. We show that syn and anti conformations of the graphene-like terminations lead to important effects in the vibrational features of the chains, detectable by the Raman light-scattering depolarization.