Ionic Interdiffusion Research Articles

Nonlinear-response-function approach to binary ionic mixtures: Dynamical theory.

The authors generalize the Golden-Kalman one-component-plasma (OCP) nonlinear-response-function approach to the formulation of a dynamical theory for binary-ionic-mixture plasmas. The principal result of the new dynamical theory is a self-consistent approximation scheme for the calculation of linear ionic polarizabilities and collective-mode structure at long wavelengths and arbitrary coupling strengths. The approximation scheme is constructed from the dynamical nonlinear fluctuation-dissipation theorem and the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) kinetic equation prepared in the velocity-average approximation (VAA). Equilibrium three-point correlations, quadratic response functions, and the dynamical superposition approximation are all central elements of the theory. The theory is exact at zero frequency and exactly reproduces the coefficients of the high-frequency-moment-sum-rule expansion through order 1/..omega../sup 4/. Collective-mode calculations based on the new approximation scheme indicate that the (positive) shift in the plasma frequency is temperature dependent at weak coupling and temperature independent at very strong coupling. These calculations, moreover, reproduce the qualitative features of the Hansen-McDonald-Vieillefosse molecular-dynamics data for the dispersion of the optical mode in the strong-coupling regime, while at the same time very nearly reproducing the weak-coupling frequency shift predicted by Baus's microscopic theory. The authors conclude that the temperature-dependent broadening and shifting of the plasma made at weak coupling is controlled primarily bymore » ionic interdiffusion transport.« less

Reaction between water and tektite glass

The reaction between water and fracture surfaces of tektite glass is studied by measuring hydrogen cocentration profiles on samples exposed to distilled water at 90 °C for times up to 1160 h. Unlike other alkali-silicate glasses studied under similar conditions, no substantial hydrated surface layers are observed. Examination under an electron microscope shows that the surface is dissolving at a rate of approximately 9 × 10−11 cm/s. The ionic exchange and interdiffusion mechanism responsible for hydration of other alkali-silicate glasses is discussed and it is concluded that the lack of hydration results from the low ionic conductivity of tektite glass.The relevance of these results to the question of the origin of the sculptured surface of tektites is discussed briefly.

Current Fluctuation Observed in Squid Ginat Axons

Current fluctuation was observed for the first time in sensitized giant axons of squid. Fluctuating current was pulsive and its number increased monotonically as the membrane system approached itself to the state of self-sustained repetitive firing of action potentials. It has been concluded that the current fluctuation is originated not from ionic interdiffusion through the membrane but from macroscopic ion-flow. This is consistent to the existence of the time-ordered and spatially-organized structure which was previously confirmed in the state of self-sustained oscillation of action potentials.