ABSTRACT
Theoretical calculations are presented on a new hypothetical 3,4-connected carbon net (called squaroglitter) incorporating 1,4 cyclohexadiene units. The structure has tetragonal space group P4/mmm (No. 123) symmetry. The optimized geometry shows normal distances, except for some elongated bonds in the cyclobutane ring substructures in the network. Squaroglitter has an indirect bandgap of about 1.0 eV. The hypothetical lattice, whose density is close to graphite, is more stable than other 3,4-connected carbon nets. A relationship to a (4,4)nanotube is explored, as is a potential threading of the lattice with metal needles.
ABSTRACT
The structures and electronic properties of a number of real and hypothetical ABX(2) compounds sharing (or evolving from) a single P4/mmm structural type are examined. These include the known CaCuO(2) and SrFeO(2) phases. A number of variations of this P4/mmm ABX(2) framework, some obvious, some exotic, all with a chemical motivation, were investigated: A = alkali metal, alkaline earth metal or La, B = Ti, Fe, Cu, or Pt, and X = C, O, S, C(2), H(2), or F. Careful attention was given to the d-orbital splitting patterns and magnetic states (ferromagnetic or antiferromagnetic) of these compounds, as well as their stability gauged by phonon dispersions and energetics. The most interesting as yet unmade compounds that emerged were (a) a carbide SrFe(C(2))(2), containing C(2) units with a C-C distance of 1.267 A, (b) an AeTiO(2) series, with Ti-Ti bonding, part sigma, part pi, tuned by the Ae(2+) cation size, and (c) NaPtF(2), for which a second structure was found, containing a hexagonal layering of (PtF(2))(-) molecules.
