Magic alkali-fullerene compound clusters of extreme thermal stability

Authors

Axel Enders, University of Nebraska-LincolnFollow
N. Malinowski, Max Planck Institute for Solid State Research
D. Ievlev, Max Planck Institute for Solid State Research
E. Zurek, Max Planck Institute for Solid State ResearchFollow
Jochen Autschbach, State University of New York, BuffaloFollow
Klaus Kern, Max Planck Institute for Solid State ResearchFollow

Date of this Version

2006

Comments

Published in THE JOURNAL OF CHEMICAL PHYSICS 125, 191102 (2006). © 2006 American Institute of Physics. Used by permission.

Abstract

The thermal stability of free pure C₆₀-, as well as C₆₀-alkali, and -alkaline-earth metal compound clusters is investigated. We find that small (C₆₀) _m-clusters (m ≤ 6) decay at comparatively low temperatures below 400 K, as a consequence of weak intermolecular van der Waals interaction. Adding barium or potassium to the clusters dramatically increases the decay temperatures for “magic” configurations of (C₆₀)_mBa_2m−1 and (C₆₀)_mK_2m, which reach values as high as 1780 K. Contrary to common belief, the superstable compound clusters are not characterized by filled geometrical or electronic shells. Density functional calculations show that the delicate interplay of ionic (K, Ba) and covalent (Ba) interaction between C₆₀ and the metal atoms, on the one hand, and entropic contributions to the Gibbs free energy, on the other hand, determine the unusual stability.