Showing papers by "Susumu Saito published in 1995"

Electronic structure of si46 and na2ba6si46

Abstract: We study solids of ${\mathrm{Si}}_{20}$ fullerenes, ${\mathrm{Si}}_{46}$ and ${\mathrm{Na}}_{2}$${\mathrm{Ba}}_{6}$${\mathrm{Si}}_{46}$, in the framework of density-functional theory. The electronic structure of ${\mathrm{Si}}_{46}$ is remarkably different from that of the diamond Si lattice due to its pentagonal network. The valence-band top becomes deeper, resulting in a narrow valence-band width and a wide fundamental gap. Also, another gap appears within the valence bands. In the Na- and Ba-codoped phase, Ba states show strong hybridization with ${\mathrm{Si}}_{46}$ states giving a very high Fermi-level density of states, which should be of essential importance for the superconductivity observed in ${\mathrm{Na}}_{\mathit{x}}$${\mathrm{Ba}}_{\mathit{y}}$${\mathrm{Si}}_{46}$.

Electronic Structure of C78 and C78-Graphite Cointercalation Compound.

Abstract: We study the electronic structure of C 78 and that of C 78 -graphite cointercalation compound First we show the electronic structure of five isomers of C 78 Their geometric structures have been optimized by an empirical model potential and their electronic structure has been calculated using the tight-binding model The C 2 v -symmetry C 78 , a major isomer experimentally extracted, is found to have a considerably deep lowest unoccupied state Using this C 2 v C 78 , we design a stage-1 C 78 -graphite cointercalation compound Its electronic structure calculated with the tight-binding model shows that the deep lowest unoccupied state of the C 2 v C 78 causes charge transfer from a graphite sheet to C 78 Although the material is formed with only carbon atoms, C 78 -graphite cointercalation compound is the hole doped graphite intercalation compound