In situ Brillouin spectroscopy of a pressure-induced apparent second-order transition in a silicate glass.
Brillouin scattering measurements of a silicate glass, carried out at high pressures in the diamond anvil cell, show a dramatic increase in the pressure dependence of longitudinal velocity, and a discontinuity in the compressibility of the glass at about 6 GPa. While a first-order phase transition has been documented under pressure within amorphous ice, we demonstrate that an apparent second-order transition to a new, structurally distinct amorphous phase can occur via the abrupt onset of a new compressional mechanism, which may be triggered by a shift in polymerization of the glass or an onset of a change in coordination of silicon, within pressurized amorphous silicates.
Tkachev
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School of Ocean and Earth Science and Technology University of Hawaii, Honolulu, Hawaii 96822, USA. stkachev@soest.hawaii.edu
Manghnani
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Williams
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