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VOLUME 62 (1995) | ISSUE 4 |
PAGE 334
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Experimental confirmation of the instability of the crystal structure of In ice prior to amorphization under pressure
Stal'gorova O. V. , Gromnitskaya E. L. , Brazhkin V. V.
The pressure dependences of the propagation velocities of transverse ultrasonic waves were determined for polycrystalline ice Ih and high-density amorphous ice (hda) in the pressure range 0-1.7 GPa at 78 K. It was determined that the velocity of ultrasound decreases significantly (—10%) in Ih ice polycrystal before amorphization (Γ=78 К, ρ =1.1 GPa) and, correspondingly, the shear modulus softens, which is an experimental indication of mechanical instability of the crystal lattice occurring as a result of solid-phase amorphization under pressure. When the amorphous ice (hda) is heated from 78 К at a pressure ρ—0.05 GPa, anomalous behavior of the transverse velocity of ultrasound is observed at temperatures of 100-130 K. This behavior is evidently associated with a phase transition of hda into amorphous low-density ice (Ida). © 1995 American Institute of Physics.
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