Structural and Magnetic Properties of sp-Hybridized Carbon

We perform extended calculations of the electronic structure and geometrical optimization of composed carbon structures where carbon acquires its sp (carbynes) or sp (graphene and aromatic components) hybrid character. We evaluate the electronic structure within the Density Functional Theory (DFT) in the Local Spin Density Approximation (LSDA), which provides a reliable estimate of the total adiabatic energy. We minimize the latter to obtain the locally stable structures and binding energies. We also evaluate magnetic structures, and, by density functional perturbation theory, vibrational properties (frequencies plus infrared and Raman intensities). We find that carbyne linear chains bind strongly to graphene and aromatic structures, usually acquiring a markedly polyynic character (large bond length alternation of single-triple bonds). Advisor: Dr. Nicola Manini Co-Advisor: Prof. Giovanni Onida