Two-dimensional molecular diffusion and phase transitions inHNO3-intercalated graphite studied by quasielastic neutron scattering

Abstract

We have observed for the first time, by incoherent quasielastic neutron scattering, a diffusive motion of a molecular unit intercalated in graphite in which both rotational and translational components are present. In the semi-incommensurate phase we observe only a rotational motion in which the number of rotating molecules depends on temperature. In the liquid phase both rotational and translational motions are observed. The latter corresponds to a jump of the molecule of 2.50±0.1 Å which is the in-plane lattice vector of the graphite layer. The translational diffusion constant shows a critical behavior.