ABSTRACT
Summary ................................................................................................. 38 2.1 Discovery of Metallic Carbon ........................................................ 38 2.2 The Glitter Model of Metallic Carbon ........................................... 41 2.3 Theoretical Stability of Glitter ....................................................... 48 2.4 Conclusions .................................................................................... 51 Keywords ................................................................................................ 53 References ............................................................................................... 53
SUMMARY OF SYNTHESIS OF GLITTER
Structural analysis on carbonaceous samples produced from high temperature-pressure conditions by Palatnik et al., in 1984 indicate the existence of a metallic allotrope of carbon with a diffraction pattern closely matching that of cubic diamond. A structure proposed for this phase by Konyashin et al., and others suggests that the four interstitial carbon atoms occupying ½ the tetrahedral holes in the ordinary cubic diamond lattice are vacant in the new structure. This leads to a transformation of the Fd3m, ordinary cubic diamond structure-type, to a simple face centered cubic carbon lattice in space group Fm3m, with a lattice parameter of 3.56 Å, identical with that of cubic diamond. The new structure supports the diffraction evidence accumulated for this so-called “n-diamond” phase, but does not hold up to a first principles total energy optimization at the DFT level of theory for the fcc lattice, which reports the Konyashin et al. structure to be unstable. Here we report an alternative tetragonal carbon structural-type, which we have called “glitter,” that explains the observed diffraction pattern of n-diamond reasonably well, and that is stabilized by extensive spiroconjugation in three dimensions leading to a metallic status for the carbonaceous structural-type.
