| | 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
| Prof, Dr, Dr | Requires cookie* | | | Title
| Aluminiumphosphate mit nichtzentrosymmetrischen Schicht-und Raumnetzstrukturen aus topologisch verwandten Motiven: 2. KA12(P 0 4 )2 (0 H )* 2 H 20 | | | | Abstract
| Alum inum Phosphates w ith N on-C entrosym m etric Layer-and Fram ew ork-Structures o f Topologically R elated M otifs: 2. K A l2(P0 4)2(0 H)-2 H 20 Stefan D icka, Gisbert G roßm annb, G isela O hm sb, M anfred M üller0 KAl2(P04)2(0 H)-2H20 was obtained by the reaction of gibbsite with a potassium-phosphate solution of pH = 5.5 at 373 K. A single crystal X-ray structure analysis showed that it is an ordered, F-free K-analog of the microporous compound AIPO4-CI2 . Crystal data: orthorhombic space group P 2 \2 \2 \, a = 920.5(1), b = 970.7(2), c = 982.8(2) pm, Z -4. The structure consists of dimeric units of AIOö octahedra and AIO5 trigonal bipyramids, bridged by an OH and two bidentate phosphate groups. The dimers are linked by phosphate to form corrugated layers which are topologically related to the layers in KAl2(P04)2(0 H)-4H20 and minyulite. The layers are connected by Al-O-P and hydrogen bonds to a three dimensional framework structure with K ions in channel-like cavities. A neutron powder scattering experiment with KAb(P04)2(0 D)-2D20 showed that the bridging OD group and only one D of each water molecule are involved in hydrogen bonding. 31P MAS NMR spectra show two isotropic lines at 6iso = —6.9 and -18,7 ppm of the intensity ratio 1:1 and confirm the presence of two crystallographically independent P atoms in the unit cell. In the 'H MAS NMR spectra the water molecules and the bridging OH group show signals at 5.9 and 1.1 ppm, respectively. | | | |
Reference
| Z. Naturforsch. 52b, 1447—1455 (1997); eingegangen am 9. September 1997 | | | |
Published
| 1997 | | | |
Keywords
| Crystal Structure, Neutron Scattering, MAS NMR, Aluminium Phosphate | | | |
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| default:Reihe_B/52/ZNB-1997-52b-1447.pdf | | | | Identifier
| ZNB-1997-52b-1447 | | | | Volume
| 52 | |
| 4 | Author
| Francoanellite K^alschpo^cpo, Stefan Dicka, Thomas Zeiskeb | Requires cookie* | | | Title
| Francoanellit K3A15HP04)6(P04)2*12H20: Struktur und Synthese durch topochemische Entwässerung von Taranakit-I 2 H2O: Structure and Synthesis by Topochemical Dehydration of Taranakite | | | | Abstract
| Single crystals of synthetic francoanellite K3Al5(HP0 4)6(P0 4)2-12H20 could be obtained for the first time by topochemical dehydration of taranakite crystals. An X-ray structure de termination showed francoanellite to be the mineral with the second longest crystallographic axis described hitherto. Crystal data: space group R3c, a = 869.0(2), c = 8227(1)pm, Z = 6 , R g = 0.042. Francoanellite is a layer structure mineral having six layers of composition [K3Al5(HP04)6(P04)2(H2 0)i2], connected by hydrogen bonds. The rigid layer is formed by columns of corner sharing hydrogen phosphate tetrahedra and AIOö-octahedra which are inter connected by additional six-coordinated A1 ions. In trigonal holes of the layer orthophosphate ions are situated. The structure of francoanellite is very similar to the structure of taranakite K3H6Al5(P04)8-18H20 which has planar water interlayers between the Al-phosphate layers. A neutron scattering experiment with subsequent Rietveld refinement of the powder pattern gave the H-atom positions. Hydrogen bonds in francoanellite are formed within the rigid layers and between them. During the reaction taranakite —► francoanellite crystals in an intermediate stage of dehy dration could be obtained. From the c-axis of 8858 pm and one-dimensional electron density projections it can be proposed that in these crystals every second water interlayer was lost and a first order staging product of the deintercalation of water from taranakite was formed. | | | |
Reference
| Z. Naturforsch. 53b, 711—719 (1998); eingegangen am 2. März 1998 | | | |
Published
| 1998 | | | |
Keywords
| Crystal Structure, Neutron Scattering, Francoanellite, Taranakite, Topochemical Reaction | | | |
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| default:Reihe_B/53/ZNB-1998-53b-0711.pdf | | | | Identifier
| ZNB-1998-53b-0711 | | | | Volume
| 53 | |
| 5 | 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 | |
| 6 | 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 | |
| 7 | Author
| StefanD. Icka, Gisbert Großmannb, G. Isela, Ohm Sb, Thom As Zeiskec | Requires cookie* | | | Title
| Aluminiumphosphate mit nichtzentrosymmetrischen Schicht-und Raumnetzstrukturen aus topologisch verwandten Motiven: 1. KA12(P 0 4)2(0H)*4H20 Aluminum Phosphates with Non-Centrosym metric Layer-and Framework-Structures o f Topologically Related Motifs | | | | Abstract
| KAl2(P04)2(0 H)-4H20 could be obtained by the reaction of gibbsite with a potassium-phosphate solution of pH = 5.5 at 333 K. A single crystal X-ray structure analysis showed that KAl2(P04)2(0 H)-4H20 is isotypic with the mineral minyulite. Crystal data: orthorhombic space group P b a l, a = 934.7(1), b = 982, 1 (1), c = 551,0(1) pm, Z = 2. It possesses dimeric units of Al-octahedra which are bridged by an OH-and two bidentate phosphate groups. The dimers are linked by phosphate to plane polar layers. Cavities in the layers are occupied by K ions. One corner of each phosphate tetrahedron is not connected to Al but accepts four hydrogen bonds from water molecules bound to Al of the adjacent layer. A powder neutron scattering experiment with KAl2(P04)2(0 D)-4D20 showed that four D atoms and P coordinate the hydrogen bond accepting O in KAl2(P04)2(0 D)-4D20 like a square pyramid. Analogous dimeric building units are found in the Al phosphate minerals minyulite and morinite; similar dimers of Fe octahedra occur in the mineral copiapite, a number of Fe containing enzymes and numerous synthetic iron complexes. High-resolution 31P solid-state NMR spectra show only one isotropic line at <5;so = —9.6 ppm and confirm the presence of one symmetry independent phosphorus site in the unit cell. In the 'H-MAS-NMR spectra the water molecules and the bridging OH groups show signals at 5.4 and 1.4 ppm, respectively. | | | |
Reference
| Z. Naturforsch. 52b, 1439—1446 (1997); eingegangen am 9. September 1997 | | | |
Published
| 1997 | | | |
Keywords
| Crystal Structure, Neutron Scattering, MAS NMR, Minyulite, Aluminium Phosphate | | | |
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| default:Reihe_B/52/ZNB-1997-52b-1439.pdf | | | | Identifier
| ZNB-1997-52b-1439 | | | | Volume
| 52 | |
| 9 | 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 | |
| 10 | 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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