Our experimental results clearly indicate that the metallization behavior of MoSe2 exhibits significant dependence on the pressure environments.

This study reported a pressure-induced metallization for molybdenum tellurium under different pressure environments up to ∼25.9 GPa through a series of experiments and first-principles theoretical calculations. This metallization was closely related to the gradual closure of bandgap rather than the structural phase transition. Under the non-hydrostatic environment, the metallization point was ∼12.5 GPa and irreversible, while it occurred at a higher pressure of ∼14.9 GPa and was reversible under the hydrostatic environment. We ascribed these discrepancies to the strong deviatoric stress, which reinforced the Te-Te interactions and caused the permanent plastic deformation of the interlayer spacing.

The structural, vibrational and electronic properties of ReS 2 were investigated up to ~34 GPa by Raman spectroscopy, AC impedance spectroscopy, atomic force microscopy and highresolution transmission electron microscopy, combining with first-principle calculations under two different pressure environments. The experimental results showed that ReS 2 endured a structural transition at ~2.5 GPa both under non-hydrostatic and hydrostatic conditions. We found that a metallization occurred at ~27.5 GPa under non-hydrostatic conditions and at ~35.4 GPa under hydrostatic conditions. The occurrence of distinct metallization point attributed to the influence of deviatoric stresses, which significantly affected the layered structure and the weak van der Waals interaction for ReS 2 .

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A crystalline to amorphous and metallic transition was demonstrated by impedance spectroscopy, Raman spectroscopy, AFM and HRTEM in DAC.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01994720.

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High–pressure phase stability of gallium phosphide was explored under different hydrostatic environments up to 40.0 GPa in a diamond anvil cell. Two irreversible phase transitions from the semiconductor to metal to an amorphous state appear at 19.8 and 31.5 GPa and as well as 22.6 and 35.3 GPa under nonhydrostatic and hydrostatic environments, respectively. Furthermore, the hysteresis effect of the high–pressure phase transition of a sphalerite–structure compound under a hydrostatic environment was disclosed. All of the obtained results can provide new insight into the underlying structural evolution and electrical transport characteristics for the semiconducting compound at different hydrostatic environments.