  The high-pressure dynamics of a computer-modeled silica melt is studied in
the framework of the mode-coupling theory of the glass transition (MCT) using
static-structure input from molecular-dynamics (MD) computer simulation. The
theory reproduces the experimentally known viscosity minimum (diffusivity
maximum) as a function of density or pressure and explains it in terms of a
corresponding minimum in its critical temperature. This minimum arises from a
gradual change in the equilibrium static structure which shifts from being
dominated by tetrahedral ordering to showing the cageing known from
high-density liquids. The theory is in qualitative agreement with computer
simulation results.

Materials Science