Band-gap tuning and linear magnetoresistance in the silver chalcogenides

Optimally doped silver selenide and silver telluride exhibit linear positive magnetoresistance over decades in magnetic field and on a scale comparable to the colossal magnetoresistance compounds. We use hydrostatic pressure to smoothly alter the band structure of Ag-rich and Ag-deficient samples of semiconducting Ag(2 +/-delta)Te of fixed stoichiometry and disorder. We find that the magnetoresistance spikes and the linear field dependence emerges when the bands cross and the Hall coefficient changes sign.

Persistence of well-defined collective excitations in a molten transition metal

Well-defined microscopic collective excitations are found in liquid Ni at 1763 K by means of inelastic neutron scattering. Such excitations are supported by the liquid despite an anharmonic character of its thermodynamic functions. Consideration of the detailed shape of the interionic pair potential provides a way to understand why atomic motions at microscopic scales behave in a way much closer to the alkali metals than to the liquefied rare gases.

Structure of liquid PEO-LiTFSI electrolyte

The structure of a polymer electrolyte, P(EO)7.5LiN(SO 2CF (3))(2), has been determined by neutron diffraction with isotropic substitution. The Li ions are bonded on average to five ether oxygens belonging to pairs of PEO coils. These are arranged with a considerable degree of extended-range order providing pathways for the Li ion conduction. The lack of ion pairing in this system below 4.8 A is reminiscent of that observed in the remarkable structure of P(EO)6LiAsF (6) and implies that anions and cations are free to migrate independently.