Density functional calculations of hypothetical neutral hollow octahedral molecules with a 48-atom framework: Hydrides and oxides of boron, carbon, nitrogen, aluminum, and silicon

We computed via first-principles density functional theory calculations (em ploying both the local density and generalized gradient approximations) the dimensions, bond lengths and angles, binding energy, and HOMO-LUMO gap of the following hypothetical neutral hollow octahedral molecules: B48H24, C48 H48, C96H80 (formed by bonding two C48H48 molecules), N48H24, Al48H24, and Si48H48; B24O24, C24O24, N24O24, Al24O24, and Si24O24. Each molecule consis ts of a large hollow framework of six puckered eight-membered rings whose p lanes are either mutually perpendicular or parallel, so that each molecule possesses only eight- and nine-membered rings. The hydrides have their hydr ogen atoms attached only to the two-atom bridging sites on the framework. T he oxides have their oxygen atoms occupying exclusively the two-atom bridgi ng sites of the framework alternating with the (B, C, N, Al, Si) atoms excl usively occupying the three-atom bridging sites. We also calculated the inf rared spectra of the C48H48 and the C24O24 molecules. For the sake of compa rison, we also examined the hypothetical octahedral C-48 fullerene cuboctoh edron (possessing four-, six-, and eight-membered rings) studied by Dunlap and Taylor. The molecules based on carbon would be the most stable; those b ased on nitrogen would be the least stable, if at all. (C) 2000 American In stitute of Physics. [S0021- 9606(00)30421-4].