High pressure synthesis of the mixed valent and nonsuperconducting ternary YbRhxSny compound

The ternary compound YbRh_1.4Sn_4.6 with the phase I structure (simple cubic) when subjected to a pressure of 40 kbar at 800°C is found to transform to phase III structure (f.c.c.) with the composition YbRh_1.1Sn₃. The latter compound has a lattice parameter of $\text{a = 13.735}\text{A}\text{?}$ which suggests that the Yb is in an intermediate valence state. The temperature dependence of magnetic susceptibility suggests that the Yb is in a homogeneously mixed valence state in the pressure synthesized product. In the phase I structure YbRh_1.1Sn_4.6 is superconducting at 8.6°K, but in the phase III structure the compound YbRh_1.1Sn₃ is not superconducting down to 0.9°K. It is suggested that superconductivity and mixed valence are incompatible.     

Features of electron density and temperature in the 500–3500 km region of the plasmasphere—(1) Dawn and dusk sectors

Dawn-dusk features of the plasmasphere are examined for intervals in February and September 1969, using electrostatic probe data ofN _e andT _e from the ISIS-I satellite. Clear plasmatrough formation is seen in the vicinity of 70° geomagnetic latitude in both dawn and dusk sectors in the 1500–3500 km region, but the plasmatrough is absent in the altitude range 500–1500 km. The plasmatrough minimum near 70°φ exhibits no asymmetry between dawn and dusk sectors in its latitudinal position. TheT _e peak associated with the plasmatrough is more pronounced in the dawn sector. DawnN _e is less than duskN _e, but dawnT _e exceeds duskT _e. The influence of processes in the magnetosphere in causing these features is examined.     

Electron transfer free radical mechanism in the reactions of arenediazonium cations with grignard reagents

The major pathway in the reactions of arenediazonium cations with certain Grignard reagents is found to involve an electron transfer from the latter to the π-system of the former reactant and radicals are the immediate precursors of the final products.     

Flow of a micropolar fluid in a tube with sinusoidal deformation

Summary The flow of a micropolar fluid for sinusoidally deforming boundaries is discussed in detail. The velocity and microrotation fields and the streamfunction are determined and plotted under the assumption of small deformations.

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Zusammenfassung Die Strömung einer mikropolaren Flïssigkeit mit sinusoidaler Verformung der Begrenzung wird ausführlich diskutiert. Die Geschwindigkeits- und Mikrorotationsfelder und die Stromfunktion werden mit der Annahme einer kleinen Verformung bestimmt und graphisch dargestellt.

     

Valence Changes at High Pressure in Systems Containing Lanthanoids

Pressure-induced valence change in samarium sulfide SmS is reminiscent of alchemy, for when the electronic transition has taken place, the originally dull looking substance glitters like gold. Although it is not the realization of the alchemist's dream in the true sense, the material in the new state exhibits extraordinarily interesting behavior. As a novel feature, the valence state of the samarium fluctuates between two electronic configurations at a very fast rate. The physical properties of systems containing lanthanoids can be profoundly altered by manipulating the valence state by pressure or by chemical substitution. These phenomena will be described and discussed in the present article.     

NDDO MO calculations: isotropic hyperfine coupling constants and nuclear spin-spin coupling constants

The nonempirical NDDO MO method in its unrestricted form has been used to evaluate isotropic hyperfine coupling constants and nuclear spin-spin coupling constants. Satisfactory agreement with INDO and experimental results is obtained.     

Optical microscopic,X-ray diffraction,and electrical resistance studies of CuCl at high pressure

Electrical resistance and X-ray diffraction measurements and also optical observations under a polarizing microscope were made on CuCl to pressures in excess of 12.5 GPa at room temperature using a diamond anvil cell. Resistance measurements were also performed in a piston-cylinder apparatus to pressures of approximately 5.5 GPa at room temperature. Three samples of CuCl prepared by different methods were examined. No anomalous pressure dependence in electrical resistance was found in the pressure range studied, and no dramatic changes in optical transmission were observed up to pressures of approximately 10.0 GPa. Optical observations and X-ray diffraction measurements indicate the existence of four phases in the pressure range studied, including a nonconducting black opaque phase which grows with time when CuCl is left for several days at the highest pressures.