Liquid metals diffraction studies

Acetylides (continued) liquid crystals, 12, 246 powder diffraction studies, 1, 586 in Ru—Os mixed-metals, 6, 1081 j2-Acetylides, in triruthenium and triosmium clusters, 6, 761... 

Electron Diffraction Study of the Structure of liquid metals and alloys. 

Takagi, M. Electron diffraction study of liquid solid transition of thin metal films. J. Phys. Soc. Japan 9, 359 (1954). 

Structural chemistry of solutions started in Japan rather late compared with other studies of solutions, although crystallographic investigations were very highly developed and actively investigated in Japan. This fact may be due to lack of the concept of structure of liquids in most Japanese physical chemists. The concept of "structure was soundly applied to solids and molecules in the gas phase, but not to liquids and solutions. X-Ray diffraction studies on liquids and amorphous substances were already examined in 1916 by Debye and Sherrer , immediately after the first work of Debye for the X-ray diffraction. Studies on liquid metals and molten salts by using X-... 

Covalent nitrates. Apart from organic nitrates covalent nitrates of non-metals are limited to those of H, F, and Cl. (CINO3 has been prepared from anhydrous HNO3 and CIF as a liquid stable at —40°C in glass or stainless steel vessels. 9 Electron diffraction studies have been made of the explosive gas FN03 and of the (planar) methyl nitrate molecule. A refinement of the crystal structure of pentaerythritol nitrate, C(CH20N02)4, shows that the nitrate group has the same structure, (d), as in nitric acid. 

X-ray diffracLion, Lhe X-rays are scattered by the electron clouds around individual atoms. Since the atoms and molecules of the liquid sample are not fixed in space, the information resulting from the diffraction experiment must be interpreted in terms of statistical averages. The neutrons used in a neutron diffraction experiment are scattered by the nuclei of the atoms in the liquid sample so that the scattering pattern is quite different from that for X-rays. In electron diffraction, the electrical potential, which depends on the spatial configuration of the nuclei and electronic density distribution, determines the diffraction pattern. Early experiments involved simple monoatomic liquids such as the inert gases and liquid metals. However, many molecular liquids have also been studied, including polar liquids such as water, the alcohols, and amides [5]. In this section, attention is focused on two of these techniques, namely. X-ray and neutron diffraction. 

Thermodynamic parameters of Mn-Si, Ag-Ge, Au-Sn, ° and Lu-Pb ° liquid metal solutions have been examined. Atomic ordering in Zn-Sn melts, assessed from the results of X-ray diffraction and adiabatic compressibility studies, has been reported it is concluded that interactions between like elements are stronger than between unlike elements, leading to positive deviations from ideality. ... 

Without the periodic array, there are no longer lattice wave numbers but a distributed structure factor S(q). The phase will vary in a complicated way, but an average measurable S (q)S(q) exists and is spherically symmetric. This is just what is needed for a calculation of the resistivity of the liquid metals. The first such calculation using pseudopotentials (Harrison, 1963b) followed an earlier and conceptually similar calculation by Ziman (1961). It involved the direct substitution of S (q)S(q), obtained by X-ray diffraction experiments on the liquid, into Eq, (16-23). Subsequently, it became clear that a theoretical form for S q)S q) given by Percus and Yevick (1958) and Percus (1962) was more convenient, and probably as accurate as the experiment for the resistivity calculation. This approach was used by Ashcroft and Lekner (1966) for an extensive study of the resistivity of all the simple liquid metals. The form due to Percus and Yevick depends only upon two parameters, a hard-sphere diameter and a packing fraction these lead to a simple form in terms of elementary functions Ashcroft and Lekner discuss the choice of parameters. This form is presumably just as appropriate for other elemental liquids. 

Most of the metal alkoxides of interest for electrooptical ceramics are solids (less often liquids) that can be purified by recrystallization, sublimation, or distillation. They are all moisture sensitive, and handling under an inert atmosphere and with anhydrous solvents is thus required. Their unequivocal characterization and formulation are best achieved by x-ray diffraction studies (on monocrystals). Studies on solutions (molecular weight data, nuclear magnetic resonance, NMR, with H, or metal nuclei) are a means either to establish whether the solid-state structure is retained or, in the absence of x-ray data, to establish the molecular structure and eventually stereolability [48]. Mass spectrometry provides information on the stability of the oligomers or the het-erometallic species in the vapor phase. The information gained by infrared spectroscopy is limited the technique is mostly useful for the identification of solvates M(OR) (ROH)x (vOH absorption 3400-3100 cm-l or of chemically modified (heteroleptic) alkoxides (probe for the vCO stretching of P-diketonate or carboxylate ligands, for instance). 

Hydrogen/deuterium isotopic substitution coupled with neutron diffraction studies have been used to show that the addition of an alkali metal to liquid NH3 disrupts the hydrogen bonding present in the solvent. In a saturated lithium-ammonia solution (21 mole percent metal), no hydrogen bonding remains between NH3 molecules. Saturated L1-NH3 solutions contain tetrahedrally coordinated Li, whereas saturated K-NH3 solutions contain octahedrally coordinated K. 

The coordination and organometallic chemistries of the lanthanoid metals are rapidly growing areas of research, and in Section 9.12, we described the recent use of ionic liquids as a medium for the synthesis of new /-block metal complexes. Since most complexes are paramagnetic, routine characterization by NMR spectroscopic methods is not usually possible. Thus, compound characterization tends to rely on X-ray diffraction studies. The paramagnetic nature of lanthanoid complexes has, however, been turned to advantage in their application as NMR shift reagents (Box 27.3) and MRl contrast agents (Box 4.3). 

Enderby, J.E., 1985, Diffraction Studies of Liquids, in Amorphous Solids and the Liquid State, eds N.H. March, R.A. Street and M. Tosi (Plenum, New York) pp. 3-30. Enderby, J.E., and R.A. Howe, 1973, The Thermoelectric Power of Liquid Metals and Alloys, in The Properties of Liquid Metals, ed. S. Takeuchi (Taylor and Francis, London) pp. 283-287. 

By means of thermal analysis, metallography and X-ray diffraction studies, Svechnikov et al. (1975) have investigated the properties of cast and annealed Nd-Yb alloys. Alloys were prepared by melting the metals in an electric arc furnace under an argon atmosphere. The interaction between the two metals was represented by a monotectic-type phase diagram (fig. 64). These two elements were found to have limited solubilities in each other in the solid state and also in the liquid state near the melting points. 

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