title: Orientational Disorder in Adamantane and Adamantanecarboxylic Acid.
abstract: The molecular crystals adamantane, C10H16, and adamantanecarboxylic acid, C10H15COOH, undergo order-disorder phase transitions at 208 and 250 K, respectively. Reverse Monte Carlo refinement of total neutron scattering data collected from deuterated samples immediately above these phase transitions shows that the high-temperature phases are well described by models in which the adamantyl groups are disordered over two sites. No correlation between the orientations of neighbouring molecules is observed. These results demonstrate that the intermolecular potential energy of these materials depends strongly on the orientation of the reference molecule but only very weakly on the orientations of its neighbours.
authors.affiliation: School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
authors.forename: Edward O R
authors.initials: EO
authors.lastname: Beake
authors.affiliation: ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, UK.|Current address: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.
authors.forename: Matthew G
authors.identifier: http://orcid.org/0000-0002-2891-7086
authors.initials: MG
authors.lastname: Tucker
authors.affiliation: School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
authors.forename: Martin T
authors.identifier: http://orcid.org/0000-0002-8030-1457
authors.initials: MT
authors.lastname: Dove
authors.affiliation: School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
authors.forename: Anthony E
authors.identifier: http://orcid.org/0000-0003-4225-0158
authors.initials: AE
authors.lastname: Phillips
keywords: adamantane; orientational disorder; plastic crystals; reverse Monte Carlo; total neutron scattering