Rotational tunnelling and methyl group reorientation in Sn(CH3)4 by inelastic neutron scattering and nuclear magnetic resonance

1983 ◽  
Vol 51 (4) ◽  
pp. 309-318 ◽  
Author(s):  
M. Prager ◽  
K. -H. Dupr�e ◽  
W. M�ller-Warmuth
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Methyl Group ◽  
Nuclear Magnetic

Ti-Zr-Ni Quasicrystals: Structure and Hydrogen Storage

1995 ◽  
Vol 400 ◽  
Author(s):  
R. M. Stroud ◽  
A. M. Viano ◽  
E. H. Majzoub ◽  
P. C. Gibbons ◽  
K. F. Kelton
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Transition Metal ◽  
Hydrogen Storage ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
X Ray ◽  
Structure And Dynamics ◽  
Icosahedral Phases

AbstractTitanium-based icosahedral phases constitute the second largest class of quasicrystals. In contrast with other Ti-based icosahedral phases (i-phases), Ti-Zr-Ni i-phases are well ordered and their formation is inhibited by the presence of Si and O, elements that stabilize the Ti-3d transition metal quasicrystals. We present x-ray and DSC data that suggest that Ti-Zr-Ni i-phases form a different class of titanium-based quasicrystals that are closely related to the MgZn2 Laves phase. The DSC data also suggest that the i-phase may be stable in these alloys. The ability of Ti-Zr-Ni i-phases to absorb up to 62 atomic % of hydrogen is presented and discussed. This opens new avenues of investigation of the structure and dynamics of quasiperiodic phases using elastic and inelastic neutron scattering and nuclear magnetic resonance and may point to potential uses for quasicrystals in hydrogen storage applications.

scholarly journals Water and Ion Dynamics in Confined Media: A Multi-Scale Study of the Clay/Water Interface

2021 ◽  
Vol 5 (2) ◽  
pp. 34
Author(s):  
Patrice Porion ◽  
Ali Asaad ◽  
Thomas Dabat ◽  
Baptiste Dazas ◽  
Alfred Delville ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Water Molecules ◽  
Bottom Up ◽  
Elastic Neutron ◽  
Multi Scale ◽  
Dynamical Properties ◽  
Nuclear Magnetic

This review details a large panel of experimental studies (Inelastic Neutron Scattering, Quasi-Elastic Neutron Scattering, Nuclear Magnetic Resonance relaxometry, Pulsed-Gradient Spin-Echo attenuation, Nuclear Magnetic Resonance Imaging, macroscopic diffusion experiments) used recently to probe, over a large distribution of characteristic times (from pico-second up to days), the dynamical properties of water molecules and neutralizing cations diffusing within clay/water interfacial media. The purpose of this review is not to describe these various experimental methods in detail but, rather, to investigate the specific dynamical information obtained by each of them concerning these clay/water interfacial media. In addition, this review also illustrates the various numerical methods (quantum Density Functional Theory, classical Molecular Dynamics, Brownian Dynamics, macroscopic differential equations) used to interpret these various experimental data by analyzing the corresponding multi-scale dynamical processes. The purpose of this multi-scale study is to perform a bottom-up analysis of the dynamical properties of confined ions and water molecules, by using complementary experimental and numerical studies covering a broad range of diffusion times (between pico-seconds up to days) and corresponding diffusion lengths (between Angstroms and centimeters). In the context of such a bottom-up approach, the numerical modeling of the dynamical properties of the diffusing probes is based on experimental or numerical investigations performed on a smaller scale, thus avoiding the use of empirical or fitted parameters.

Rotational Excitations and Tunneling of Nonequivalent Methyl Groups in Tetramethylstibonium Iodide as Studied by Nuclear Magnetic Resonance and Inelastic Neutron Scattering

1991 ◽  
Vol 46 (9) ◽  
pp. 759-769 ◽  
Author(s):  
Günter Burbach ◽  
Alarich Weiss
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperatures ◽  
Inelastic Neutron Scattering ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Methyl Group ◽  
Spin Lattice

Abstract Nuclear magnetic resonance (NMR) and inelastic neutron scattering techniques (INS) have been applied to study the rotational motions and methyl group tunneling in tetramethylstibonium iodide, [Sb(CH3)4 ] I, over er a wide temperature range. Parameters describing the [Sb(CH3)4]+ cation tumbling and the methyl group reorientation at high temperatures and quantum mechanical tunneling of the methyl groups at low temperatures were determined. The results for INS and NMR experiments at low temperatures can be explained in terms of two crystallographically inequivalent methyl groups CH3(1) and CH3(2), which were established earlier by the crystal structure determination. In the INS spectra two tunneling lines at 22.0 μeV for CH3(1) and 1.05 μeV for CH3(2) with inelastic intensities in the ratio 3:1 were observed at T = 4 K. The activation energies derived from proton NMR spin-lattice relaxation time measurements for the thermally activated methyl group rotation are 1.50 kJ/mol for CH3(1) and 3.81 kJ/mol for CH3(2). They are in accordance with the activation energies obtained from neutron fixed-window measurements. The activation energy for [Sb(CH3)4]+ cation tumbling is 50.9 kJ/mol as determined from the high temperature spin-lattice relaxation behaviour. Rotational potentials for the methyl groups are derived. For both kinds of inequivalent methyl groups the threefold potential terms dominate; three- and sixfold potential contributions are shifted by 180°

FORMATION OF DIASTEREOISOMERIC ORTHOACETATES OF D-MANNOSE: N.M.R. SPECTRAL EVIDENCE

1963 ◽  
Vol 41 (2) ◽  
pp. 399-406 ◽  
Author(s):  
A. S. Perlin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Acid Hydrolysis ◽  
Chemical Shifts ◽  
Isomer Ratio ◽  
Methyl Group ◽  
Major Isomer ◽  
Spectral Evidence ◽  
Ratio Data ◽  
Nuclear Magnetic

Diastereoisomeric 1,2-orthoacetates of D-mannose are formed under conditions of the Königs–Knorr synthesis. This is shown by the isolation of two crystalline isomers of β-D-mannose 1,2-(benzyl orthoacetate), and also by examination of the nuclear magnetic resonance (n.m.r.) spectra of several D-mannose orthoacetates. The diastereoisomers show notable differences in respective chemical shifts for the C-methyl and other protons and these variations, together with isomer-ratio data, suggest that the major isomer of a given pair possesses the configuration in which the C-methyl group is endo- and the OR group is exo-. On acid hydrolysis the orthoacetates yield mainly 2-O-acetyl-D-mannose, the structure of which is confirmed by n.m.r. spectral evidence.

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