Computer modelling of thorium doping in LiCaAlF(6) and LiSrAlF(6): application to the development of solid state optical frequency devices.

This paper describes computer modelling of thorium doping in crystalline LiCaAlF(6) and LiSrAlF(6). The study has been motivated by the interest in using these materials as hosts for (229)Th nuclei, which are being investigated for use as frequency standards. The dopant sites and form of charge compensation are obtained; this information is essential for the further development and optimization of these devices.

Isolation, characterization, and ecology of sulfur-respiring crenarchaea inhabiting acid-sulfate-chloride-containing geothermal springs in Yellowstone National Park.

Elemental sulfur (S(0)) is associated with many geochemically diverse hot springs, yet little is known about the phylogeny, physiology, and ecology of the organisms involved in its cycling. Here we report the isolation, characterization, and ecology of two novel, S(0)-reducing Crenarchaea from an acid geothermal spring referred to as Dragon Spring. Isolate 18U65 grows optimally at 70 to 72 degrees C and at pH 2.

Computer modelling of mixed metal fluorides for optical applications.

This paper describes a new computational method for predicting the optical behaviour of doped inorganic materials. There is considerable interest in using inorganic materials in photonic devices, and in many cases, the optical properties of these materials depend on doping by ions such as those from the rare earth series. Among the inorganic materials of interest are the mixed metal fluorides (e.

Lanthanide transport in stabilized zirconias: interrelation between ionic radius and diffusion coefficient.

The diffusion of all stable lanthanides was measured both in calcia stabilized zirconia (CSZ) and in yttria stabilized zirconia (YSZ) in the temperature range between 1,286 and 1,600 degrees C. The lanthanide diffusion coefficients obtained increase with increasing ionic radius. The experimental activation enthalpy of diffusion is near 6 eV for CSZ and between 4 and 5 eV for YSZ and is not strongly affected by the type of lanthanide.