By examining rate measurements for two amorphous SiO 2 glasses we find, instead, a paradox. As a consequence, dissolution rates of amorphous phases should simply scale linearly with increasing driving force (undersaturation) through the higher probability of detaching silica tetrahedra. This would seem to imply amorphous phases have surfaces that are disordered at an atomic scale so that the transfer of SiO 4 tetrahedra to solution always leaves the surface free energy of the solid unchanged. The mechanisms by which amorphous silica dissolves have proven elusive because noncrystalline materials lack the structural order that allows them to be studied by the classical terrace, ledge, kink-based models applied to crystals.
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