Barrelenes/tubelenes — a new class of cage carbon molecules and its solids

Abstract

We discuss a new class of non-spherical cage carbon clusters — barrelenes — which manifest themselves in a stable or metastable solid phase. They present a cylindrical graphite surface with an elemental frame-belt of 2 m ( m=5, 6, 7, …) carbon atoms and two spherical-like appropimate lids. As an example, the barrelenes C 24+12 n ( n is the number of belts, m=6 is the number of carbon hexagons in a belt) and C 60+18 n ( m=9) are analyzed in detail. The possible types of lids are described: closed — bowl-shaped, partially open — collar-shaped, and corresponding clusters: (a) b-C N barrelenes — barrel-shaped ( n < m) clusters with closed lids; (b) j-C N jarenes — jar-shaped ( n < m) clusters with one partially open lid; (c) m-C N muffenes — muff-shaped ( n < m) cl usters with both lids open; (d) t-C N tubelens — tube-like ( n ⩾ m) clusters with any kind of lids. The main Kekulé structures of such clusters are analyzed. Possible b-C N and t-C N solids and their doped analogues are discussed including the properties of an isolated long ( n ⪢ m) tubelene which is a quasi-one-dimensional solid. The physical properties of such solids (conduction anisotropy, local piezoelectric-like effect, optic non-linearity, possible superconductivity) are considered.