Lattice dynamics of a rotor-stator molecular crystal: Fullerene-cubaneC60⋅C8H8

Abstract

The dynamics of fullerene-cubane ͑C 60 ·C 8 H 8 ͒ cocrystal is studied combining experimental ͓x-ray diffuse scattering, quasielastic and inelastic neutron scattering ͑INS͔͒ and simulation ͑molecular dynamics͒ investigations. Neutron scattering gives direct evidence of the free rotation of fullerenes and of the libration of cubanes in the high-temperature phase, validating the "rotor-stator" description of this molecular system. X-ray diffuse scattering shows that orientational disorder survives the order/disorder transition in the low-temperature phase, although the loss of fullerene isotropic rotational diffusion is featured by the appearance of a 2.2 meV mode in the INS spectra. The coupling between INS and simulations allows identifying a degeneracy lift of the cubane librations in the low temperature phase, which is used as a tool for probing the environment of cubane in this phase and for getting further insights into the phase transition mechanism.

Parent and reduced graphene oxide of different origin in light of neutron scattering

“…Taken together, the ILL carbon data exhibit changes in the G(ω) spectra when going from macroscopic graphite to mesoscopic ball-milled graphite and nanoscopic TEGO, thus disclosing changes in the behavior of graphite-like phonon modes due to decreasing size parameters [31]. Clearly, while G(ω) spectrum of graphite (a) significantly reproduces all the features of the calculated density of states (DOS) of graphite [33] the reduced dimensions of the grains in bill-milled graphite (b) and TEGO (c) have strong effects on the dynamic properties: peaks in the density of states progressively broaden, with an increased proportion in the low frequency part of the spectrum [31].…”

From a one-dimensional crystal to a one-dimensional liquid: A comprehensive dynamical study of C60peapods

“…The quantity measured in a TOF experiment is the double differential scattering cross section, proportional to the dynamical structure factor S(Q,ω). 30,31 The S(Q,ω) function corresponds to the space-time Fourier transform of the pair correlation function G(r,t), and represents therefore a physical observable bridging the gap between the microscopic theoretical description and the macroscopic experimental measurements. As G(r,t) contains both "self" and "distinct" contributions, S(Q,ω) consists of both incoherent and coherent terms, 30 and single-particle and collective contributions could partially overlap.…”

Mechanisms of the rotational dynamics of C70 in C70-cubane heteromolecular crystals

“…[10][11][12] Computational studies have also been performed for C 60 -cubane crystals and have provided useful insights to the interpretation of the experimental observations. [13][14][15][16] In our previous work, 13 we have investigated the dynamics of C 60 -cubane cubic crystal using classical molecular dynamics (MD) and studied the high-temperature polymerization process and electronic properties using tight-binding reactive MD. In this work, we extend upon these studies by carrying out MD simulations of C 70 -cubane crystals to characterize the reorientational ordering and dynamics of C 70 fullerenes and cubane molecules in the cubic and tetragonal rotor-stator phases of the crystal.…”