ELASTIC-WAVE VELOCITIES OF HIGH-DENSITY PRESSURE-INDUCED AMORPHOUS GEO2

Two samples of amorphous GeO2 were prepared at room temperature by compression of alpha-quartz type crystals at 13 and 20GPa. The former sample has a density of 4.42(6) Mg/m3 and the latter 5.34(2) Mg/m3. The elastic wave velocities, vp and vs of each sample were measured under pressures up to 4GPa at room temperature. The results are: (1) Both vp and vs are faster in the sample with higher density. (2) Even the velocities of the sample with lower density are faster than those of both alpha-quartz type crystal and a conventional amorphous phase whose density is less than 4Mg/m3. Since the pressure derivative of vp is larger than that of vs, the difference between vp and vs becomes greater with increasing pressure.