Electronic structure and mechanical stability of the graphitic honeycomblattice

A family of crystal structures of carbon composed of alternating sp2 and sp3 bonds is investigated. Graphitic strips are connected by sp3 bonds to form an array of hexagonal pillars exhibiting a honeycomb lattice in the perpendicular plane. The electronic structure and elastic properties of this family of structures are calculated using an ab initio pseudopotential as well as the environment-dependent tight-binding method. Their electronic structure has a similar size dependence to zigzag nanotubes; they are metallic if twice the strip width is a multiple of three hexagonal units, and otherwise semiconducting with a wider range of the band gap than for carbon nanotubes. The structural stability is studied and compared with other carbon structures.open252

Direct determination of molecular constants from rovibronic spectra with genetic algorithms

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Polymorphism of scyllo-inositol: joining crystal structure prediction with experiment to elucidate the structures of two polymorphs

ABSTRACT: We report on the crystal structures of two polymorphs of scyllo-inositol. Crystallization of this inositol initially failed to yield a single crystal suitable for structure solution, so a computational prediction of the low-energy forms was performed in parallel with the crystallization experiments. When a single crystal was finally grown, its structure failed to explain the powder X-ray diffraction pattern of the bulk material, which seemed to show a mixture of polymorphs. With the aid of the lowest-energy predicted crystal structure from a lattice energy search and the DASH program for structure solution from powder data, we propose the structure of the second polymorph. The combined use of single-crystal structure solution, structure solution from powder diffraction data, and a lattice energy search for possible structures, which was necessary for the elucidation of the second polymorph of scyllo-inositol, demonstrates the synergy between experimental and computational studies of molecular organic materials