Comment on "Metallization of Fluid Nitrogen and the Mott Transition in Highly Compressed Low-Z Fluids"

A comment on ``Metallization of Fluid Nitrogen and the Mott Transition in Highly Compressed Low-Z Fluids'' by Chau et al, Phys. Rev. Lett. 90, 245501 (2003).Comment: Submitted to PR

Freezing Kinetics in Overcompressed Water

We report high pressure dynamic compression experiments of liquid water along a quasi-adiabatic path leading to the formation of ice VII. We observe dynamic features resembling Van der Waals loops and find that liquid water is compacted to a metastable state close to the ice density before the onset of crystallization. By analyzing the characteristic kinetic time scale involved we estimate the nucleation barrier and conclude that liquid water has been compressed to a high pressure state close to its thermodynamic stability limit

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

We report the first experimental evidence for a metallic phase in fluid molecular oxygen. Our electrical conductivity measurements of fluid oxygen under dynamic quasi-isentropic compression show that a non-metal/metal transition occurs at 3.4 fold compression, 4500 K and 1.2 Mbar. We discuss the main features of the electrical conductivity dependence on density and temperature and give an interpretation of the nature of the electrical transport mechanisms in fluid oxygen at these extreme conditions.Comment: RevTeX, 4 figure

Near-Equilibrium Polymorphic Phase Transformations in Praseodymium Under Dynamic Compression

We report the first experimental observation of sequential, multiple polymorphic phase transformations occurring in Praseodymium dynamically compressed using a ramp wave. The experiments also display the signatures of reverse transformations occuring upon pressure release and reveal the presence of small hysteresys loops. The results are in very good agreement with equilibrium hydrodynamic calculations performed using a thermodynamically consistent, multi-phase equation of state for Praseodymium, suggesting a near-equilibrium transformation behavior

Electrical conductivity of lithium at megabar pressures

We report measurements of the electrical conductivity of a liquid alkali metal - lithium - at pressures up to 1.8 Mbar and fourfold compression, achieved through shock compression experiments. We find that the results are consistent with a departure of the electronic properties of lithium from the nearly free electron approximation at high pressures.Comment: RevTex, 4 pages, 4 figure

CsBi ₄ Te ₆ : A High-Performance Thermoelectric Material for Low-Temperature Applications

Thermoelectric (Peltier) heat pumps are capable of refrigerating solid or fluid objects, and unlike conventional vapor compressor systems, they can be miniaturized without loss of efficiency. More efficient thermoelectric materials need to be identified, especially for low-temperature applications in electronics and devices. The material CsBi 4 Te 6 has been synthesized and its properties have been studied. When doped appropriately, it exhibits a high thermoelectric figure of merit below room temperature (ZT max ∼0.8 at 225 kelvin). At cryogenic temperatures, the thermoelectric properties of CsBi 4 Te 6 appear to match or exceed those of Bi 2– x Sb x Te 3– y Se y alloys. </jats:p