Water-like transport property anomalies in liquid silicates investigated at high T and P by computer simulation techniques.

The P-dependence of the liquid structure and diffusion dynamics of Na₂O-SiO₂ binary solutions and jadeite at 6000 K was studied using a multicomponent ion-dynamics computer simulation. In liquid jadeite, P increases cause sharp increases in the diffusivities of Al, Si and O ions; a maximum diffusivity (implying a minimum viscosity) was found near 300 kbar. For Na⁺, however, the pressure coefficient is strongly negative. In the binary silicate solutions, there was a decrease in anomalous P-induced increases in diffusivity as Na₂O increased. At low P the coordination numbers of Si and Al are both 4, but these increase systematically with increase in P, reaching average values of 5 for Si at approx max. oxygen diffusivity. -R.A.H.