Dynamical molecular disorder and diffuse scattering in an alkane/urea incommensurate inclusion compound

• Published in: The European physical journal. B, Condensed matter physics Vol. 24; no. 1; pp. 51 - 57
• Main Authors: LEFORT, R, TOUDIC, B, ETRILLARD, J, GUILLAUME, F, BOURGES, P, CURRAT, R, BRECZEWSKI, T
• Format: Journal Article
• Language: English
• Published: Les Ulis Springer 01-11-2001; Berlin EDP sciences; Springer-Verlag
• Subjects: Condensed Matter; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Lattice dynamics; Materials Science; Other topics in lattice dynamics; Physics; Molecular motion; Incommensurate phases; Alkanes; Isotopic species; Experimental study; Coherent scattering; Form factors; Diffuse scattering; Neutron diffusion; Molecular rotation; Urea; Monocrystals; Inelastic scattering; Lattice dynamics; Inclusion compounds; Incoherent scattering; Organic compounds
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1007/s100510170021

The diffraction pattern of n-alkane/urea inclusion compounds is known to contain a broad diffuse scattering related to the molecular form factor of the alkane species, indicating individual rotational and/or translational disorder of these molecules. Inelastic coherent neutron scattering reveals for the first time the entirely dynamical character of the alkane molecular disorder around room temperature. This observation fully agrees with a recent model of the coherent scattering cross section of totally uncorrelated motions. In the ordered phase this diffuse scattering remains, but elastic, and very low energy molecular vibrational modes are evidenced. These observations are discussed in relation with previous incoherent neutron scattering results.