Coupling to haloform molecules in intercalated C60?

For field-effect-doped fullerenes it was reported that the superconducting transition temperature Tc is markedly larger for C60.2CHX_3 (X=Cl, Br) crystals, than for pure C60. Initially this was explained by the expansion of the volume per C60-molecule and the corresponding increase in the density of states at the Fermi level in the intercalated crystals. On closer examination it has, however, turned out to be unlikely that this is the mechanism behind the increase in Tc. An alternative explanation of the enhanced transition temperatures assumes that the conduction electrons not only couple to the vibrational modes of the C60-molecule, but also to the modes of the intercalated molecules. We investigate the possibility of such a coupling. We find that, assuming the ideal bulk structure of the intercalated crystal, both a coupling due to hybridization of the molecular levels, and a coupling via dipole moments should be very small. This suggests that the presence of the gate-oxide in the field-effect-devices strongly affects the structure of the fullerene crystal at the interface.Comment: 4 pages, 1 figure, to be published in PRB (rapid communication

Crystal Structures and Electronic Properties of Haloform-Intercalated C60

Using density functional methods we calculated structural and electronic properties of bulk chloroform and bromoform intercalated C60, C60 2CHX3 (X=Cl,Br). Both compounds are narrow band insulator materials with a gap between valence and conduction bands larger than 1 eV. The calculated widths of the valence and conduction bands are 0.4-0.6 eV and 0.3-0.4 eV, respectively. The orbitals of the haloform molecules overlap with the $\pi$ orbitals of the fullerene molecules and the p-type orbitals of halogen atoms significantly contribute to the valence and conduction bands of C60 2CHX3. Charging with electrons and holes turns the systems to metals. Contrary to expectation, 10 to 20 % of the charge is on the haloform molecules and is thus not completely localized on the fullerene molecules. Calculations on different crystal structures of C60 2CHCl3 and C60 2CHBr3 revealed that the density of states at the Fermi energy are sensitive to the orientation of the haloform and C60 molecules. At a charging of three holes, which corresponds to the superconducting phase of pure C60 and C60 2CHX3, the calculated density of states (DOS) at the Fermi energy increases in the sequence DOS(C60) < DOS(C60 2CHCl3) < DOS(C60 2CHBr3).Comment: 11 pages, 7 figures, 4 table

Phase transitions of co-intercalated c-60 crystals

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Room temperature large-scale synthesis of layered frameworks as low-cost 4V cathode materials for lithium ion batteries

10.1038/srep16270Scientific Reports51627

Compressibility of co intercalated c-60 crystals

Contains fulltext : 98953.pdf (publisher's version ) (Closed access

Crystal Structure of a Rigid Ferrocence-based Macrocycle from High-Resolution X-ray Powder Diffraction.

NoA macrocycle, 6, has been synthesized in high yield from 2,5-di(pyrazol-1-yl)hydroquinone and 1,1`-fc[B(Me)NMe2]2 {fc = Fe(C5H4)2}. The molecule incorporates two redox-active 1,1`-ferrocenylene units in its backbone and contains four chiral boron centers, each of them possessing the same configuration. It is demonstrated that crystal structures of organometallics of moderate complexity can be solved from high-resolution X-ray powder diffraction patterns, once the connectivity between the functional groups is known

Extraordinary anisotropic thermal expansion in photosalient crystals

10.1107/S2052252519014581IUCrJ783-8

Green and rapid mechanosynthesis of high-porosity NU- and UiO-type metal-organic frameworks

The use of a dodecanuclear zirconium acetate cluster as a precursor enables the rapid, clean mechanochemical synthesis of high-microporosity metal-organic frameworks NU-901 and UiO-67, with surface areas up to 2250 m2 g-1. Real-time X-ray diffraction monitoring reveals that mechanochemical reactions involving the conventional hexanuclear zirconium methacrylate precursor are hindered by the formation of an inert intermediate, which does not appear when using the dodecanuclear acetate cluster as a reactant. © 2018 The Royal Society of Chemistry