| | 1 | Author
| RalphO. Simmons | Requires cookie* | | | Title
| Single-Particle Momentum Distributions from Deep Inelastic Neutron Scattering (DINS)  | | | | Abstract
| Single-particle longitudinal momentum distributions in condensed matter are now accessible to direct measurement using eV neutrons. Some systems of particular interest include a) quantum solids and fluids, formed from "Hie, 4 He, and H 2 , b) prototype molecular crystals, formed from noble gases, c) fluids such as H 2 and Ne, which show deviations from classical behavior and d) mixed systems, in which guest-host interactions may be important. Quantum solids can be investigated at substan-tially different densities, for different structures, and further, can be compared to the corresponding fluids, with which they have significant similarities in their single-particle properties such as their momentum distributions. Noble gas solids comprise a graduated family with progressively varying importance of zero-point energy, of phonon anharmonicity, and of multi-body forces. They have also been very useful for matrix isolation studies, and eV neutron scattering can yield their center-of-mass motions, not previously seen directly. Finally, noble gas fluids can be used to investigate the nature and extent of final-state effects in the neutron scatttering. Such effects are defined to be the difference between the longitudinal "neutron Compton profile" and the longitudinal momentum distribution. | | | |
Reference
| Z. Naturforsch. 48a, 415—424 (1993); received December 27 1991 | | | |
Published
| 1993 | | | |
Keywords
| Momentum distribution, Dynamics, Neutron scattering | | | |
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| default:Reihe_A/48/ZNA-1993-48a-0415.pdf | | | | Identifier
| ZNA-1993-48a-0415 | | | | Volume
| 48 | |
| 2 | Author
| Uwe Hoppe, Rainer Kranold, Emil Gattefa, Jörg Neuefeindb, DavidA. Keenc | Requires cookie* | | | Title
| An X-ray and Neutron Scattering Study of the Structure of Zinc Vanadate Glasses | | | | Abstract
| The short-range order of vitreous V20 5 and of three (Zn0)Jt(V20 5)1_x glasses with x = 0.2, 0.4, and 0.5 is studied by X-ray and neutron diffraction experiments where the change of the contrast allows to resolve the V -0 and Z n -0 correlations. The V -0 and the Z n -0 first-neighbor peaks are approximat ed by several Gaussian functions. In case of vitreous V20 5 two obvious V -0 distances exist which are related with V 0 4 and V 0 5 units. With ZnO additions the V -O coordination number decreases from 4.4 in vitreous V20 5 to 4.0 in the metavanadate glass where the strongest decrease of the fraction of V 0 5 units is found for glasses of * < 0.2. Dominantly, the V 0 5 groups are linked with the neighboring units by comers. The Z n-0 coordination numbers of the modified glasses are about five with closest dis tances of = 0.200 nm. | | | |
Reference
| Z. Naturforsch. 56a, 478—4 (2001); received April 3 2001 | | | |
Published
| 2001 | | | |
Keywords
| Neutron Scattering, X-ray Scattering, Short-range Order, Vanadate Glasses | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0478.pdf | | | | Identifier
| ZNA-2001-56a-0478 | | | | Volume
| 56 | |
| 3 | Author
| E. Mikuli, A. Migdał-Mikuli, I. Natkaniec, J. Mayer | Requires cookie* | | | Title
| Phase Transitions and Water Dynamics of [Mn(H 2 0) 6 ](C10 4 ) 2 Studied by Differential Scanning Calorimetry and Neutron Scattering Methods | | | | Abstract
| DSC measurements performed at 95 -290 K have shown that [Mn(H 2 0) 6 ](C10 4) 2 possesses, besides a high-temperature phase, existing above 323 K, four low-temperature solid phases. The inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) pat-terns registered at 20 -290 K have supported the DSC results and provided evidence that the investigated substance possesses even more than five solid phases. The IINS spectra have shown that in the room-temperature phase, water molecules perform fast stochastic reorientation at the picosecond scale. The orientational disorder characteristic for the room-temperature phase can be easily overcooled and frozen. Even by relatively slow cooling at ca. 40 K/hour a metastable, orientational (protonic) glass phase is formed below ca. 160 K. Below ca. 100 K, a structural phase transition was observed by the NPD, however the IINS spectra indicate existence of the pure ordered low-temperature phase only after annealing the sample for a few hours at 100 K. On heating, a structural phase transition takes place at ca. 120 K, and at ca. 225 K water molecules begin fast reorientation. | | | |
Reference
| Z. Naturforsch. 55a, 759—764 (2000); received July 7 2000 | | | |
Published
| 2000 | | | |
Keywords
| Hexaaquamanganese(II) chlorate(VII), Phase Transitions, DSC, Neutron Scattering | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0759.pdf | | | | Identifier
| ZNA-2000-55a-0759 | | | | Volume
| 55 | |
| 4 | Author
| Z. Naturforsch | Requires cookie* | | | Title
| A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses | | | | Abstract
| Diffraction experiments were performed on two (Nd203)x(P205)i_ x glasses for studying the en vironmental order of the Nd3+ cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the N d-0 and 0 -0 first neighbor peaks. An N d-0 coordination number of 6.6±0.3 and a mean N d-0 distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the N d-0 coordination number is equal to the number of terminal oxygen atoms (0 T) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all 0 T's are in N d-0T-P positions. In the metaphosphate glass the NdO" polyhedra have to share some 0 T sites. | | | |
Reference
| Z. Naturforsch. 56a, 237—243 (2001); received January 8 2001 | | | |
Published
| 2001 | | | |
Keywords
| Neutron Scattering, X-ray Scattering, Short-range Order, Phosphate Glasses | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0237.pdf | | | | Identifier
| ZNA-2001-56a-0237 | | | | Volume
| 56 | |
| 6 | Author
| E. Mikuli, A. Migdał-Mikuli, I. Natkanieca, B. Grad | Requires cookie* | | | Title
| Phase Transitions and Water Dynamics of [Co(H20 ) 6](C104)2 and [Mn(H20 ) 6](BF4)2 Studied by Neutron Scattering Methods | | | | Abstract
| Inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) patterns, registered for [Co(H20) 6](C104)2 at 18 -270 K and for [Mn(H20) 6](BF4)2 at 18 -230 K, provided evidence that these crystals possess three solid phases in these ranges of temperatures. In both compounds the phase transition occurring at T C3 is connected with a change of the crystal structure, and that occurring at T C2 with a change in the rate of the reorientational motions of H20 ligands. | | | |
Reference
| Z. Naturforsch. 56a, 244 (2001); received December 12 2000 | | | |
Published
| 2001 | | | |
Keywords
| Hexaaquacobalt(II) chlorate(VII) and Hexaaquamanganese(II) tetrafluoroborate, Phase Transitions, Structural Changes, Water Reorientation, Neutron Scattering | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0244.pdf | | | | Identifier
| ZNA-2001-56a-0244 | | | | Volume
| 56 | |
| 7 | Author
| P. Andonov, H. E. Fischer3 ', P. Palleau3, S. Kimurab | Requires cookie* | | | Title
| Structural Study of Liquid Lithium Niobate by Neutron Diffraction Role of the Li Atom in the Clustering Near Solidification | | | | Abstract
| The structure of liquid LiNb03 has been investigated by neutron diffraction using samples with dif ferent isotopic composition of lithium. The intensity scattered by these samples has been measured for momentum transfers 0.4 A-1 < Q < 17.1 Ä-1 and temperatures 1600 K>T> 1500 K, which include the undercooling domain. From an analysis of the correlation functions Gt j (r) of the atomic pairs Li-Li, Li-Nb, Li-O and their structural evolutions, given by A G,_v (r) = G,_j (r)1500 -G,_, (r)1550 made with reference to the crystalline LiNb03 ferroelectric structure, it was possible to confirm a local ordering similar to that of the crystal. The presence of clusters (groupings of N b 03 octahedra) is confirmed. Both regular and irregular N b06 octahedra are observed in the liquid near solidification. With its high mobil ity in the melt, the Li atom plays an important role in the clustering: the Li— O and Li— Nb bonds make possible the staking of four octahedra groups into clusters of eight octahedra or more. The Li-Li bonds join these groups. The diameter of the clusters is a least 22 A in the undercooling regime. | | | |
Reference
| Z. Naturforsch. 56a, 395—406 (2001); received February 12 2001 | | | |
Published
| 2001 | | | |
Keywords
| Structure of Liquids, Neutron Scattering, Atomic Clusters, Liquid Lithium Niobate | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0395.pdf | | | | Identifier
| ZNA-2001-56a-0395 | | | | Volume
| 56 | |
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