Hydrogen Motion In Lanthanum Hydrides By Means Of Quasielastic Neutron Scattering

1998 ◽  
Vol 513 ◽  
Author(s):  
C. Karmonik ◽  
T. J. Udovic ◽  
J. J. Rush
Keyword(s):  
Neutron Scattering ◽  
Long Range ◽  
Powder Diffraction ◽  
Octahedral Site ◽  
Translational Diffusion ◽  
Neutron Powder Diffraction ◽  
Neutron Spectra ◽  
Different Temperatures ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

ABSTRACTThe hydrogen dynamics in LaHx was studied for different concentrations x ≥ 2.5 at different temperatures by quasielastic neutron scattering. The neutron spectra show the existence of both long-range translational diffusion and localized motion. The prefactor of the jump rate for the first process exhibits a maximum around x= 2.75. The radius for the second motion is in agreement with neutron powder diffraction measurements which support a localized motion of H confined in an octahedral site.

Localized Diffusional Motion of Hydrogen and Deuterium in Crystalline Pd9Si2

1998 ◽  
Vol 527 ◽  
Author(s):  
C. Karmonik ◽  
Q. Huang ◽  
T.J. Udovic ◽  
J.J. Rush ◽  
Y. Andersson ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Spectroscopic Measurements ◽  
Temporal Parameters ◽  
Quasielastic Neutron ◽  
Diffusional Motion ◽  
Quasielastic Neutron Scattering

ABSTRACTUsing quasielastic neutron scattering, we have studied the dynamics of hydrogen and deuterium in crystalline Pd9Si2. For both isotopes, a localized motion was found which takes place between two energetically different sites. For the hydrogenated sample, the spatial and temporal parameters characterizing this motion are derived. The results are in agreement with neutron powder diffraction and neutron vibrational spectroscopic measurements.

ANISOTROPY OF TRANSLATIONAL DIFFUSION IN PREMELTED METHANE FILMS

1997 ◽  
Vol 04 (05) ◽  
pp. 863-868 ◽  
Author(s):  
P. STOCKER ◽  
J.-M. GAY ◽  
M. BIENFAIT ◽  
G. CODDENS
Keyword(s):  
Neutron Scattering ◽  
Translational Diffusion ◽  
Surface Melting ◽  
Diffusion Anisotropy ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

Surface melting of the (111) face of methane films adsorbed on graphite is investigated by quasielastic neutron scattering with special attention paid to translational diffusion within the liquid-like layer parallel and normal to the surface. The comparison of the experimental spectra measured in different geometries clearly shows diffusion anisotropy. Simulations of the data provide an estimation of the anisotropy as a function of temperature.

Structure and Dynamics of Propylene Oxide and Trimethylene Oxide Clathrate Hydrates

2004 ◽  
Vol 840 ◽  
Author(s):  
Inmaculada Peral ◽  
Joseph E. Curtis ◽  
Bryan C. Chakoumakos ◽  
Camille Y. Jones
Keyword(s):  
Neutron Scattering ◽  
Propylene Oxide ◽  
Neutron Powder Diffraction ◽  
Clathrate Hydrates ◽  
Cyclic Ethers ◽  
Structure And Dynamics ◽  
Trimethylene Oxide ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering ◽  
Dynamics Simulations

ABSTRACTWe present results from studies of the structure and dynamics of clathrate hydrates of three cyclic ethers by neutron diffraction and preliminary results on molecular dynamics simulations. Recent results from neutron powder diffraction and quasielastic neutron scattering of studies of propylene oxide (PO, C3H6O) and its isomer trimethyelene oxide (TMO, C3H6O), are compared with structural results obtained previously for tetrahydrofuran (THF, C3H5O). Experimental evidence of distortions of the host structures with temperature is discussed in light of the findings from quasielastic neutron scattering, which indicate distinct regions of high-temperature and low-temperature rotational dynamics and a temperature dependence related to the size of the guest. Preliminary MD results indicate a general expansion of the lattice with temperature resulting in increased volume available to PO.

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