dc.contributor.author | Haarmann, F. | en_US |
dc.contributor.author | Jacobs, H. | en_US |
dc.contributor.author | Kockelmann, W. | en_US |
dc.contributor.author | Senker, J. | en_US |
dc.contributor.author | Muller, P. | en_US |
dc.contributor.author | Kennedy, CA | en_US |
dc.contributor.author | Marriott, RA | en_US |
dc.contributor.author | Qiu, L. | en_US |
dc.contributor.author | White, MA | en_US |
dc.date.accessioned | 2013-08-23T15:58:39Z | |
dc.date.available | 2013-08-23T15:58:39Z | |
dc.date.issued | 2002-09 | en_US |
dc.identifier.citation | Reproduced from Haarmann, F., H. Jacobs, W. Kockelmann, J. Senker, et al. 2002. "Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations." Journal of Chemical Physics 117(10): 4961-4972, with the permission of AIP Publishing. | en_US |
dc.identifier.issn | 0021-9606 | en_US |
dc.identifier.uri | http://dx.doi.org/10.1063/1.1479141 | en_US |
dc.identifier.uri | http://hdl.handle.net/10222/36147 | |
dc.description.abstract | Protonated and deuterated samples of the hydrogensulfide of cesium were studied by
high-resolution neutron powder diffraction, calorimetry and proton NMR investigations in a wide
temperature range. Primarily due to reorientational disorder of the anions, three modifications of
the title compounds are known: an ordered low-temperature modification-LTM (tetragonal, I4/m, Z=8),
a dynamically disordered middle-temperature modification-MTM (tetragonal, P4/mbm, Z=2), and a
high-temperature modification-HTM (cubic, Pm (3) over barm, Z=1). The LTMreversible arrowMTM phase
transition is continuous. Its order parameter, related to an order/disorder and to a displacive part
of the phase transition, coupled bilinearly, follows a critical law. The critical temperature
T-C=123.2+/-0.5 K determined by neutron diffraction of CsDS is in good agreement with T-C=121+/-2 K
obtained by calorimetric investigations. For the protonated title compound a shift to T-C=129+/-2 K
was observed by calorimetric measurements. The entropy change of this transition is (0.24+/-0.04) R
and (0.27+/-0.04) R for CsHS and CsDS, respectively. The MTMreversible arrowHTM phase transition is
clearly of first order. The transition temperatures of CsHS and CsDS are T=207.9+/-0.3 K and
T=213.6+/-0.3 K with entropy changes of (0.86+/-0.01) R and (0.81+/-0.01) R, respectively. Second
moments (M-2) of the proton NMR absorption signal of MTM and HTM are in reasonable agreement with
M-2 calculated for the known crystal structures. A minimum in spin-lattice relaxation times (T-1) in
the MTM could not be assigned by dipolar coupling to a two-site 180degrees reorientation of the
anions, a model of motion presumed by the knowledge of the crystal structure. The activation
enthalpies determined by fits of T-1 presuming a thermal activated process are in the order of
molecular reorientations (E-a=13.5+/-0.5 kJ mol(-1) for the MTM and E-a=9.3+/-0.3 kJ mol(-1) for the
HTM). In the HTM at T>330 K translational motion of the cations determines T-1 (E-a=13.8+/-0.4 kJ
mol(-1)). | en_US |
dc.relation.ispartof | Journal of Chemical Physics | en_US |
dc.title | Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray
diffraction, calorimetry and proton NMR investigations | en_US |
dc.type | article | en_US |
dc.identifier.volume | 117 | en_US |
dc.identifier.issue | 10 | en_US |
dc.identifier.startpage | 4961 | en_US |