Pressure-induced structural change of intermediate-range order in poly(4-methyl-1-pentene) melt.

High-pressure in situ x-ray diffraction and specific-volume measurements on isotactic poly(4-methyl-1-pentene) melt have uncovered abrupt changes in the pressure dependence of microscopic structure as well as that of macroscopic density. The first sharp diffraction peak of the polymer melt, which is related to the intermediate-range order and is explained as resulting from the correlations between main chains, is suppressed at pressures less than 1 kbar. These changes in intermediate-range order show similarities to those seen in liquid-liquid or amorphous-amorphous transitions in simpler small molecule based systems, suggesting that this kind of phenomenon may occur in a wide range of materials.

Complete assignment of the vibrational modes of C60 by inelastic neutron scattering spectroscopy and periodic-DFT.

In this paper we exploit the complementarity of inelastic neutron scattering (INS), infrared and Raman spectroscopies with ab initio calculations to generate an updated assignment of the vibrational modes of C(60). We have carried out periodic-DFT calculations of the high temperature face centred cubic phase modelled as the standard structure and also of the low temperature simple cubic phase, the latter for the first time. Our assignment differs from all previous work, however, it is the only one that is able to successfully reproduce the INS spectrum in terms of both transition energies and intensities.

Probing the binding and spatial arrangement of molecular hydrogen in porous hosts via neutron Compton scattering.

The adsorption of molecular hydrogen (H2) in the alkali-graphite intercalate KC24 has been studied using simultaneous neutron diffraction and Compton scattering. Neutron Compton scattering data for the (H2)xKC24 system (x = 0-2.5) were measured at T = 1.

Quantum delocalization of molecular hydrogen in alkali-graphite intercalates.

The adsorption of molecular hydrogen (H2) in the graphite intercalation compound KC24 is studied both experimentally and theoretically. High-resolution inelastic neutron data show spectral features consistent with a strong pinning of H2 along a single axis. First-principles calculations provide novel insight into the nature of H2 binding in intercalates but fail to account for the symmetry of the H2 orientational potential deduced from experiment.

Inelastic neutron scattering and Raman spectroscopies and periodic DFT studies of Rb(2)PtH(6) and Rb(2)PtD(6).

The present work has provided a complete set of assignments for the vibrational spectrum of Rb(2)PtH(6) and Rb(2)PtD(6). To confirm the assignments, a periodic density functional theory (DFT) code has been applied to the analysis of the inelastic neutron scattering (INS) spectrum of an ionic material for the first time. The work has also provided an explanation for the unusual infrared spectrum of the potassium salt.