First X-ray diffraction analysis of pressure polymerized C ₆₀ single crystals

Abstract

It is shown that C60 single crystals can be polymerized under relatively modest pressure-temperature conditions. The resulting single crystals exhibit long-range order and they are made up of 12 orientation variants. The structure is orthorhombic with a short intermolecular distance along the chains (9.14 Å), characteristic of covalent bonding. We propose a structural mechanism for the polymerization of fullerene-based compounds; it involves a shift of one of the (111) cubic planes together with a shortening of the (111) spacing. The configuration of the polymer chains presents interesting relations with that found in the A1C60 polymer compounds.

Far-infrared vibrational properties of high-pressure high-temperatureC60polymers and theC60Long1, Musfeldt2, Kamarás3 et al. 2000Phys. Rev. B292330View full textAdd to dashboardCite

“…18 In addition, the 2ϩ2-connected 1D orthorhombic chains can be made with charged C 60 's by intercalation of C 60 with alkali-metal ions (A n C 60 with nϭ1). 8,9 These charged 1D chains are structurally indistinguishable, by x-ray diffraction, 10,19 from the neutral 1D chains made by HPHT processes. Finally, the charged C 60 dimer with an atom-atom connection may be made by quenching AC 60 , 6 and more exotic atom-atom phases have been created in Na 4 C 60 and Na 2 RbC 60 .…”

“…1.͒ Charged C 60 's polymerize with the same 2ϩ2 cycloaddition connections, or by forming atom-atom connections, each consisting of one C-C bond between neighboring C 60 's. The observed polymerized C 60 structures include dimers 6,7 orthorhombic onedimensional ͑1D͒ chains, [8][9][10] tetragonal and rhombohedral two-dimensional ͑2D͒ lattices, 4,11 and some disordered 3D structures, 12 among others. 13 Methods of preparing the 2 ϩ2 cycloaddition dimer include mechanochemical reaction of C 60 with KCN or Li, 7,14 high-temperature phototransformation, 15 quasihydrostatic compression, 16 and pressurization of the template compound (ET) 2 C 60 .…”

Far-infrared vibrational properties of linearC60polymers: A comparison between neutral and charged materials

“…These two materials are known to be nearly isostructural. 3,16,17 Furthermore, the Raman spectra of the neutral and charged O polymers exhibit essentially a one-toone correspondence between peaks, with only a modest broadening and redshifting of the spectral lines of the charged polymer. 43 Still, the modest broadening and redshifting in the Raman spectrum do leave open the possibility that vibronic coupling may play a small role in the dynamics of RbC 60 , so the distinct differences in the two IR spectra of Fig.…”

“…The polymerization reaction can be carried out using both physical ͑pressure, temperature, light͒ and chemical ͑doping͒ methods, resulting in neutral and charged polymers, respectively. Under hightemperature and high-pressure ͑HTHP͒ conditions, onedimensional orthorhombic, [1][2][3][4] ͑O͒ and two-dimensional tetragonal 1,5,6 ͑T͒ and rhombohedral 1,7,8 ͑R͒ phases have been prepared. In these materials, the fullerene building blocks are connected by four-membered rings, formed via 2ϩ2 cycloaddition.…”

“…14 and 15͒ and the HTHP O polymer is a true insulator, x-ray diffraction confirms that they have similar structures. 3,16,17 Both consist of linear chains of fullerene molecules with D 2h on-ball symmetry connected by 2ϩ2 cycloaddition ͓Fig. 1͑a͔͒, but in the AC 60 O polymer, each ball formally has one excess delocalized negative charge.…”