Abstract
The structural, vibrational, and electronic characteristics in orpiment were performed in the diamond anvil cell (DAC), combined with a series of experimental and theoretical research, including Raman spectroscopy, impedance spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and first-principles theoretical calculations. The isostructural phase transition at ~25.0 GPa was manifested as noticeable changes in the compressibility, bond lengths, and slope of the conductivity, as well as in a continuous change in the pressure dependence of the unit cell volume. Furthermore, a pressure-induced metallization occurred at ~42.0 GPa, accompanied by reversible electrical conductivity. We also determined the metallicity of orpiment at 45.0 GPa by first-principles theoretical calculations, and the results were in good agreement with the results of the temperature-dependent conductivity measurements. The HRTEM and AFM images of the recovered sample confirmed that orpiment remains in the crystalline phase with an intact layered structure and available crystal-shaped clusters. These high-pressure behaviors of orpiment present some crucial information on the structural phase transition, metallization, amorphization and superconductivity for the A2B3-type of engineering materials at high pressure.
Highlights
A2 B3 -type chalcogenides with diverse structures and physical properties could be exploited in some important industrial applications, such as thermoelectric devices, solid-state power devices, refrigerating devices, photovoltaic cells, spintronics, and quantum computation [1,2,3,4]
Orpiment crystallizes in a quasi-two-dimensional monoclinic structure (SG P21 /c, Z = 4), in which the layers parallel to the (010) plane are bonded by weak van der Waals forces [8]
This meant that this sample became metal above 41.9 GPa, which was in good agreement with the electrical conductivity measured results
Summary
A2 B3 -type chalcogenides with diverse structures and physical properties could be exploited in some important industrial applications, such as thermoelectric devices, solid-state power devices, refrigerating devices, photovoltaic cells, spintronics, and quantum computation [1,2,3,4]. The type of phase transition can be determined by the characteristic parameter variations, such as variation in the unit cell volume, crystalline lattice parameters, axial ratio and bond lengths [22,23] These characteristic parameters can be obtained by first-principles theoretical calculations. To verify whether orpiment undergoes a pressure-induced phase transition above 16 GPa, the characteristic crystal cell parameters should be calculated in a large pressure range. To systematically investigate the pressure-induced phase transition and metallization of orpiment, we determined the electrical and structural properties at pressures up to ~46.0 GPa using the DAC in conjunction with a series of experimental and theoretical methods, including Raman spectroscopy, impedance spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and first-principles theoretical calculations
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