title: Experimental and theoretical investigations of the thermodynamic stability of Ba-c(60) and K-C(60) compound clusters.
abstract: A novel experimental set-up was used to study superstable (magic) Ba-C(60) and K-C(60) compound clusters. The most stable systems observed cannot be rationalized by simple electronic or by geometrical shell filling arguments. Annealing the clusters past the temperature necessary for the fragmentation of the initial metastable clusters formed at the source reveals information about their thermodynamic stability. Higher temperatures yield larger species, suggesting that similar experiments may be used to rationally produce nanoscale clusters with highly desirable properties. Density functional calculations reveal ionic (K, Ba) and covalent (Ba) bonding between C(60) and the metal atoms. The entropic contribution to the Gibbs free energy is shown to be essential in determining absolute and relative cluster stabilities. In particular, we demonstrate that at higher temperatures the entropy favors the formation of larger clusters. A simple criterion which may be used to determine the absolute and relative stabilities of general multicomponent clusters is proposed.
authors.affiliation: Max-Planck-Institut für Festkorperforschung, Heisenbergstrasse 1, 70569, Stuttgart, Germany. e.zurek@fkf.mpg.de
authors.forename: Eva
authors.initials: E
authors.lastname: Zurek
authors.forename: Jochen
authors.initials: J
authors.lastname: Autschbach
authors.forename: Nikola
authors.initials: N
authors.lastname: Malinowski
authors.forename: Axel
authors.initials: A
authors.lastname: Enders
authors.forename: Klaus
authors.initials: K
authors.lastname: Kern
mesh_terms: D001464:Barium / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D037741:Fullerenes / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D011188:Potassium / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D037741:Fullerenes; D046911:Macromolecular Substances; D001464:Barium; C069837:fullerene C60; D011188:Potassium