Pseudocarbynes: Charge-Stabilized Carbon Chains.

Carbyne is the long-sought linear allotrope of carbon. Despite many reports of solid carbyne, the evidence is unconvincing. A recent report of supposed carbyne shows gold clusters in transmission electron microscopy (TEM) images. In order to determine the effects of such clusters, we performed ab initio calculations of uncapped and capped linear carbon chains and their complexes with gold clusters. The results indicate that gold dramatically alters the electron densities of the C≡C bonds. The resulting charge-stabilization of the carbon chains leads to pseudocarbynes. These findings are corroborated in calculations of the structures of crystals containing isolated carbon chains and those intercalated with gold clusters. Calculated Raman spectra of these pseudocarbynes with gold clusters are in better agreement with experiment than calculated spectra of isolated carbon chains. The current work opens the way toward the design and development of a new class of metal-intercalated carbon compounds.