title: Probing the thermal stability and the decomposition mechanism of a magnesium-fullerene polymer via X-ray Raman spectroscopy, X-ray diffraction and molecular dynamics simulations.
abstract: We report the microscopic view of the thermal structural stability of the magnesium intercalated fullerene polymer Mg2C60. With the application of X-ray Raman spectroscopy and X-ray diffraction, we study in detail the decomposition pathways of the polymer system upon annealing at temperatures between 300 and 700 °C. We show that there are at least two energy scales involved in the decomposition reaction. Intermolecular carbon bonds, which are responsible for the formation of a 2D fullerene polymer, are broken with a relatively modest thermal energy, while the long-range order of the original polymer remains intact. With an increased thermal energy, the crystal structure in turn is found to undergo a transition to a novel intercalated cubic phase that is stable up to the highest temperature studied here. The local structure surrounding magnesium ions gets severely modified close to, possibly at, the phase transition. We used density functional theory based calculations to study the thermodynamic and kinetic aspects of the collapse of the fullerene network, and to explain the intermediate steps as well as the reaction pathways in the break-up of this peculiar C60 intermolecular bonding architecture.
authors.affiliation: Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, P.O. Box 64 00014 Helsinki, Finland. matteo.aramini@helsinki.fi simo.huotari@helsinki.fi.
authors.forename: Matteo
authors.initials: M
authors.lastname: Aramini
authors.affiliation: Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, P.O. Box 64 00014 Helsinki, Finland. matteo.aramini@helsinki.fi simo.huotari@helsinki.fi.
authors.forename: Johannes
authors.initials: J
authors.lastname: Niskanen
authors.affiliation: Institut Laue Langevin, BP 156, 71 Avenue des Martyrs, 38000, Grenoble, France and Dipartimento di Fisica e Scienze della Terra, Università degli studi di Parma, Viale delle Scienze 7/a, 43124 Parma, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cavallari
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università degli studi di Parma, Viale delle Scienze 7/a, 43124 Parma, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Pontiroli
authors.affiliation: Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, P.O. Box 64 00014 Helsinki, Finland. matteo.aramini@helsinki.fi simo.huotari@helsinki.fi.
authors.forename: Abdurrahman
authors.initials: A
authors.lastname: Musazay
authors.affiliation: ESRF - The European Synchrotron, CS40220, 38043, Grenoble, Cedex 9, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Krisch
authors.affiliation: Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, P.O. Box 64 00014 Helsinki, Finland. matteo.aramini@helsinki.fi simo.huotari@helsinki.fi.
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.affiliation: Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, P.O. Box 64 00014 Helsinki, Finland. matteo.aramini@helsinki.fi simo.huotari@helsinki.fi.
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari