Suchergebnisse

The structural and vibrational properties of bismuth selenide (Bi2Se3) have been studied by means of x-ray diffraction and Raman scattering measurements up to 20 and 30 GPa, respectively. The measurements have been complemented with ab initio total-energy and lattice dynamics calculations. Our experimental results evidence a phase transition from the low-pressure rhombohedral (R-3m) phase (B-Bi2Se3) with sixfold coordination for Bi to a monoclinic C2/m structure (B-Bi2Se3) with sevenfold coordination for Bi above 10 GPa. The equation of state and the pressure dependence of the lattice parameters and volume of a and B phases of Bi2Se3 are reported. Furthermore, the presence of a pressure-induced electronic topological phase transition in B-Bi2Se3 is discussed. Raman measurements evidence that Bi2Se3 undergoes two additional phase transitions around 20 and 28 GPa, likely toward a monoclinic C2/c and a disordered body-centered cubic structure with 8-fold and 9- or 10-fold coordination, respectively. These two high-pressure structures are the same as those recently found at high pressures in Bi2Te3 and Sb2Te3. On pressure release, Bi2Se3 reverts to the original rhombohedral phase after considerable hysteresis. Symmetries, frequencies, and pressure coefficients of the Raman and infrared modes in the different phases are reported and discussed. ; This work was done under financial support from Spanish Ministry of Science and Innovation under Projects No. MAT2007-66129, No. MAT2010-21270-C04-03/04, and No. CSD-2007-00045 and from the Valencian government under Project No. Prometeo/2011-035. It is also supported by the Ministry of Education, Youth and Sports of the Czech Republic Project No. MSM 0021627501.

The structural and vibrational properties of bismuth selenide (Bi 2Se 3) have been studied by means of x-ray diffraction and Raman scattering measurements up to 20 and 30 GPa, respectively. The measurements have been complemented with ab initio total-energy and lattice dynamics calculations. Our experimental results evidence a phase transition from the low-pressure rhombohedral (R-3m) phase (¿-Bi 2Se 3) with sixfold coordination for Bi to a monoclinic C2/m structure (ß-Bi 2Se 3) with sevenfold coordination for Bi above 10 GPa. The equation of state and the pressure dependence of the lattice parameters and volume of ¿ and ß phases of Bi 2Se 3 are reported. Furthermore, the presence of a pressure-induced electronic topological phase transition in ¿-Bi 2Se 3 is discussed. Raman measurements evidence that Bi 2Se 3 undergoes two additional phase transitions around 20 and 28 GPa, likely toward a monoclinic C2/c and a disordered body-centered cubic structure with 8-fold and 9- or 10-fold coordination, respectively. These two high-pressure structures are the same as those recently found at high pressures in Bi 2Te 3 and Sb 2Te 3. On pressure release, Bi 2Se 3 reverts to the original rhombohedral phase after considerable hysteresis. Symmetries, frequencies, and pressure coefficients of the Raman and infrared modes in the different phases are reported and discussed. © 2011 American Physical Society. ; This work was done under financial support from Spanish Ministry of Science and Innovation under Projects No. MAT2007-66129, No. MAT2010-21270-C04-03/04, and No. CSD-2007-00045 and from the Valencian government under Project No. Prometeo/2011-035. It is also supported by the Ministry of Education, Youth and Sports of the Czech Republic Project No. MSM 0021627501. E.P.G. acknowledges the financial support of the Spanish Ministry of Education. Supercomputer time was provided by the Red Espanola de Supercomputacion and the MALTA cluster. ; Vilaplana Cerda, RI.; Santamaría-Pérez, D.; Gomis Hilario, O.; Manjón Herrera, FJ.; ...