Abstract
The pressure dependent Raman scattering in the potassium molybdenum
oxide hydrate crystal, K2Mo2O7 center dot H2O, was measured. The high
pressure Raman study showed, that the compound remains in the triclinic
structure within the 0.0-3.81 GPa range and undergoes a structural phase
transition between 3.81 and 4.13 GPa. This particular phase transition
is most likely connected with changes in the Raman spectrum, in which
the number of modes associated originally with the stretching vibrations
in the MoO5 and MoO6 units is increased. However, the phase at
atmospheric pressure shows bands due to the presence of only one
equivalent site, while in the high-pressure phase, two bands are
associated with the stretching modes. Continuing the pressure evolution
up to 17.04 GPa, two further phase transitions occurred in this crystal
in the 6.3-8.1 GPa and the 12.3-14.0 GPa range, respectively. The Raman
spectra measured at about 17.04 GPa presented a crystal structure, which
experienced a pre-amorphization with a total loss of all lattice modes.
This particular result is indicative that this material may have
undergone a complete amorphization at pressures larger than 17.04 GPa.
Then, the reversible character in the triclinic P-1 (C-i(1)) structure
was recovered after releasing the pressure. (C) 2016 Elsevier B.V. All
rights reserved.
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