The Microscopic Diamond Anvil Cell: Stabilization of Superhard, Superconducting Carbon Allotropes at Ambient Pressure

Abstract

AbstractA metallic, covalently bonded carbon allotrope is predicted via first principles calculations. It is composed of an sp3 carbon framework that acts as a diamond anvil cell by constraining the distance between parallel cis‐polyacetylene chains. The distance between these sp2 carbon atoms renders the phase metallic, and yields two well‐nested nearly parallel bands that cross the Fermi level. Calculations show this phase is a conventional superconductor, with the motions of the sp2 carbons being key contributors to the electron–phonon coupling. The sp3 carbon atoms impart superior mechanical properties, with a predicted Vickers hardness of 48 GPa. This phase, metastable at ambient conditions, could be made by on‐surface polymerization of graphene nanoribbons, followed by pressurization of the resulting 2D sheets. A family of multifunctional materials with tunable superconducting and mechanical properties could be derived from this phase by varying the sp2 versus sp3 carbon content, and by doping.