How Multivalency controls Ionic Criticality

To understand how multivalency influences the reduced critical temperatures, Tce (z), and densities, roce (z), of z : 1 ionic fluids, we study equisized hard-sphere models with z = 1-3. Following Debye, Hueckel and Bjerrum, association into ion clusters is treated with, also, ionic solvation and excluded volume. In good accord with simulations but contradicting integral-equation and field theories, Tce falls when z increases while roce rises steeply: that 80-90% of the ions are bound in clusters near T_c serves to explain these trends. For z \neq 1 interphase Galvani potentials arise and are evaluated.Comment: 4 pages, 4 figure

Aging and ultra-slow equilibration in concentrated colloidal hard spheres

We study the dynamic behaviour of concentrated colloidal hard spheres using Time Resolved Correlation, a light scattering technique that can detect the slow evolution of the dynamics in out-of-equilibrium systems. Surprisingly, equilibrium is reached a very long time after sample initialization, the non-stationary regime lasting up to three orders of magnitude more than the relaxation time of the system. Before reaching equilibrium, the system displays unusual aging behaviour. The intermediate scattering function decays faster than exponentially and its relaxation time evolves non-monotonically with sample age.Comment: Submitted to the proceedings of the 6th EPS Liquid Matter Conference, Utrecht 2-6 July 200

Exact aymptotic expansions for the thermodynamics of hydrogen gas in the Saha regime

We consider the hydrogen quantum plasma in the Saha regime, where it almost reduces to a partially ionized atomic gas. We briefly review the construction of systematic expansions of thermodynamical functions beyond Saha theory, which describes an ideal mixture of ionized protons, ionized electrons and hydrogen atoms in their ground-state. Thanks to the existence of rigorous results, we first identify the simultaneous low-temperature and low-density limit in which Saha theory becomes asymptotically exact. Then, we argue that the screened cluster representation is well suited for calculating corrections, since that formalism accounts for all screening and recombination phenomena at work in a more tractable way than other many-body methods. We sketch the corresponding diagrammatical analysis, which leads to an exact asymptotic expansion for the equation of state. That scaled low-temperature expansion improves the analytical knowledge of the phase diagram. It also provides reliable numerical values over a rather wide range of temperatures and densities, as confirmed by comparisons to quantum Monte Carlo data.Comment: 10 page

Electrostatic potential of phase boundary in Coulomb systems

Any interface boundary in an equilibrium system of Coulomb particles is accompanied by the existence of a finite difference in the average electrostatic potential through this boundary. This interface potential drop is a thermodynamic quantity. It depends on temperature only and does not depend on surface properties. The zero-temperature limit of this drop (along coexistence curve) is an individual substance coefficient. The drop tends to zero at the critical point of the gas-liquid phase transition. A special critical exponent can be defined to describe this behavior. The value of the discussed potential drop is directly calculated by numerical simulation of phase transitions in Coulomb systems. Properties of the interface potential drop are discussed for several simplified Coulomb models (melting and evaporation in the One Component Plasma (OCP)). Some examples of phase transition in real situations are also discussed

Thermodynamic Model of Solid Non-Stoichiometric Uranium Dioxide

A thermodynamic description of the imperfect and nonstoichiometric ionic solid is obtained accounting for short- and long-ranged inter-ionic forces, as well as for formation of Frenkel defects. Both Coulomb and short-range interactions between defects are encompassed in a highly non-ideal ionic system where interactions of Frenkel defects are taken into account explicitly as short-ranged interactions of quasi-dipoles.JRC.E.3-Materials researc

Thermodynamic Model of Solid Non-Stoichiometric Uranium Dioxide.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

The Equation of State of UO2.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Improved Ionic Model of Liquid Uranium Dioxide.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe