LDF Electronic Structure of Fullerene Tubules

Abstract

The synthesis of macroscopic amounts of the fullerenes C₆₀ and C₇₀ and the availability of these materials has led to an explosive growth of research efforts in novel all-carbon materials.^1,2 Less than two years ago Iijima³ reported the novel synthesis based on the techniques used for fullerene synthesis of substantial quantities of multiple-shell graphitic tubules with diameters of nanometer dimensions. These tubule diameters were more than an order of magnitude smaller than those typically obtained using routine synthetic methods for graphite fibers.^4,5 This work has been widely confirmed in the literature, with subsequent work by Ebbesen and Ajayan⁶ demonstrating the synthesis of bulk quantities of these materials. More recent work has further demonstrated the synthesis of abundant amounts of single-shell graphitic tubules with diameters on the order of one nanometer.^7,8 These developments have and will stimulate many additional studies of the mechanical and electronic properties of these novel fibers. Already theoretical studies of the individual hollow concentric graphitic tubules, which comprise these fibers, predict that these nanometer-scale diameter tubules will exhibit conducting properties ranging from metals to moderate bandgap semiconductors depending on their radii and helical structure.^9–16 Other theoretical studies have shown that these tubules should have the high strengths and rigidity that their graphitic and tubular structure implies.^17,20 The metallic tubules— termed serpentine¹⁷—have also been predicted to be stable against a Peierls distortion at and far below room temperature.⁹ The fullerene tubules show the promise of an array of all-carbon structures that exhibit a broad range of electronic and structural properties, making these materials an important synthetic target for the current decade.