Structural, Vibrational, and Electronic Study of α-As2Te3 under Compression

We report a study of the structural, vibrational, and electronic properties of layered monoclinic arsenic telluride (alpha-As2Te3) at high pressures. Powder X-ray diffraction and Raman scattering measurements up to 17 GPa have been complemented with ab initio total-energy, lattice dynamics, and electronic band structure calculations. Our measurements, which include previously unreported Raman scattering measurements for crystalline alpha-As2Te3, show that this compound undergoes a reversible phase transition above 14 GPa at room temperature. The monoclinic crystalline structure of alpha-As2Te3 and its behavior under compression are analyzed by means of the compressibility tensor. Major structural and vibrational changes are observed in the range between 2 and 4 GPa and can be ascribed to the strengthening of interlayer bonds. No evidence of any isostructural phase transition has been observed in alpha-As2Te3. A comparison with other group 15 sesquichalcogenides allows understanding the structure of alpha-As2Te3 and its behavior under compression based on the activity of the cation lone electron pair in these compounds. Finally, our electronic band structure calculations show that alpha-As2Te3 is a semiconductor at 1 atm, which undergoes a trivial semiconducting-metal transition above 4 GPa. The absence of a pressure-induced electronic topological transition in alpha-As2Te3 is discussed.