Stable structures of exohedrally decorated C60-fullerenes

Abstract

A good hydrogen storage material should adsorb hydrogen in high concentrations and with optimal binding energies. Exohedrally metal decorated carbon fullerene structures were proposed as a promising material in this context. We present a fully ab-initio, unbiased structure search of the configurational space of decorated C 60 fullerenes and find that many of the hitherto postulated ground state structures are not ground states. We determine the energetically lowest configurations for decorations with a varying number of decorating atoms (2 n 32) for alkali metals, alkaline-earth metals as well as some other important elements and find that the dense uniform distribution of the decorating atoms over the surface of the C 60 , desired for hydrogen storage, can be obtained only for a few elements. An understanding of the behavior of the decorating atoms can be obtained by analyzing their bonding characteristics via the electron localization function.

Influence of an external electric field on the potential-energy surface of alkali-metal-decorated C60

“…Such a C n− 60 (where n = 2,3,4) structure is short lived [54,55], but can be stabilized by an Li + [28,56]. This explains the experimentally observed [57] and theoretically confirmed [29] homogeneous absorption of up to 12 Li atoms on C 60 . Hence, to alter this distribution pattern, a high electric field is required.…”

“…Hence, to alter this distribution pattern, a high electric field is required. The configurations that are provided in our previous work [29] are the most stable configurations up to a field strength of 1 × 10 −3 a.u. for Li 4 and 3 × 10 −3 a.u.…”

“…From our previous calculations, we know that alkali-metal atoms, except for Li, prefer to adsorb on the hexagonal site [29]. The potential-energy surface can be altered by applying an external electric field and desired configurations can be stabilized.…”

“…In previous work, we have observed that Li and K atoms prefer to homogeneously distribute over C 60 up to 12 and 6 atoms, respectively, in the absence of an external electric field [29]. For this reason we have limited the present PES scan to this maximum number of atoms.…”

Stability of Coinage Metals Interacting with C60

“…Although there are many experimental studies available on endohedral fullerenes, only few experimental investigations have been reported on exohedral fullerenes [26,27,28]. Nevertheless, numerous theoretical simulations have been performed to study interactions of metal atoms on the surface of C 60 [29,30,31,32]. Exohedral adsorption of a single atom and multiple atoms were studied by Sankar De et al [29] using ab initio simulation in the absence of dispersion correction.…”