Phonon study of rhombohedral BS under high pressure (original) (raw)
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Boron phosphide under pressure: In situ study by Raman scattering and X-ray diffraction
Journal of Applied Physics, 2014
Cubic boron phosphide BP has been studied in situ by X-ray diffraction and Raman scattering up to 55 GPa at 300 K in a diamond anvil cell. The bulk modulus of B 0 = 174(2) GPa has been established, which is in excellent agreement with our ab initio calculations. The data on Raman shift as a function of pressure, combined with equation-of-state data, allowed us to estimate the Grüneisen parameters of the TO and LO modes of zinc-blende structure, γ G TO = 1.16 and γ G LO = 1.04, just like in the case of other A III B V diamond-like phases, for which γ G TO > γ G LO 1. We also established that the pressure dependence of the effective electro-optical constant is responsible for a strong change in relative intensities of the TO and LO modes from I TO /I LO ~0.25 at 0.1 MPa to I TO /I LO ~2.5 at 45 GPa, for which we also find excellent agreement between experiment and theory.
Raman scattering study of SbSBr at high pressure
Physical Review B, 1989
The vibrational properties of the quasi-one-dimensional crystal SbSBr have been studied by Raman scattering as a function of pressure up to 21 GPa. Compressibilities parallel and perpendicular to the chain axis were measured by a microphotographic technique. This pressure study on onedimensional crystals shows the very high stability of this structure. It also shows that the highpressure behavior of the modes helps in the identification of the modes symmetry.
Structural and vibrational study of Bi_{2}Se_{3} under high pressure
Physical Review B, 2011
We report an experimental and theoretical lattice dynamics study of bismuth telluride (Bi 2 Te 3 ) up to 23 GPa together with an experimental and theoretical study of the optical absorption and reflection up to 10 GPa. The indirect bandgap of the low-pressure rhombohedral (R-3m) phase (α-Bi 2 Te 3 ) was observed to decrease with pressure at a rate of −6 meV/GPa. In regard to lattice dynamics, Raman-active modes of α-Bi 2 Te 3 were observed up to 7.4 GPa. The pressure dependence of their frequency and width provides evidence of the presence of an electronic-topological transition around 4.0 GPa. Above 7.4 GPa a phase transition is detected to the C2/m structure. On further increasing pressure two additional phase transitions, attributed to the C2/c and disordered bcc (Im-3m) phases, have been observed near 15.5 and 21.6 GPa in good agreement with the structures recently observed by means of x-ray diffraction at high pressures in Bi 2 Te 3 . After release of pressure the sample reverts back to the original rhombohedral phase after considerable hysteresis. Raman-and IR-mode symmetries, frequencies, and pressure coefficients in the different phases are reported and discussed.
High-Pressure Studies of Bi 2 S 3
The Journal of Physical Chemistry A, 2014
The high-pressure structural and vibrational properties of Bi 2 S 3 have been probed up to 65 GPa with a combination of experimental and theoretical methods. The ambient-pressure Pnma structure is found to persist up to 50 GPa; further compression leads to structural disorder. Closer inspection of our structural and Raman spectroscopic results reveals notable compressibility changes in specific structural parameters of the Pnma phase beyond 4−6 GPa. By taking the available literature into account, we speculate that a second-order isostructural transition is realized near that pressure, originating probably from a topological modification of the Bi 2 S 3 electronic structure near that pressure. Finally, the Bi 3+ loneelectron pair (LEP) stereochemical activity decreases against pressure increase; an utter vanishing, however, is not expected until 1 Mbar. This persistence of the Bi 3+ LEP activity in Bi 2 S 3 can explain the absence of any structural transitions toward higher crystalline symmetries in the investigated pressure range.
Pramana, 2012
In this paper we present the results obtained from first-principles calculations of the effect of hydrostatic pressure on the structural, elastic and electronic properties of (B3) boron phosphide, using the pseudopotential plane-wave method (PP-PW) based on density functional theory within the Teter and Pade exchange-correlation functional form of the local density approximation (LDA). The lattice parameter, molecular and crystal densities, near-neighbour distances, independent elastic constants, bulk modulus, shear modulus, anisotropy factor and energy bandgaps of (B3) BP under high pressure are presented. The results showed a phase transition pressure from the zinc blende to rock-salt phase at around 1.56 Mbar, which is in good agreement with the theoretical data reported in the literature.
Structural phase transitions in Bi2Se3 under high pressure
Scientific reports, 2015
Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. It is worthy to note that the disordered BCC phase at 27.8 GPa is not...
Raman spectroscopy ofB12As2andB12P2up to 120 GPa: Evidence for structural distortion
Physical Review B, 2010
We report results of Raman spectroscopy studies on single crystals of B 12 P 2 and B 12 As 2 under pressure to 120 GPa at 300 K. In the 75-85 GPa range in both compounds several additional modes appear while several other split. These results evidence a transition to a distorted structure with a strong deformation of the icosahedra. The Raman spectra measured at ambient down from 120 GPa show that this transformation is reversible.
Journal of Alloys and Compounds, 2011
The structural, electronic, mechanical properties and hardness of orthorhombic B 28 and tetragonal B 48 boron phases have been studied by first-principles of pseudopotential calculations. The results indicated that both boron phases are energetically and also mechanically stable. In addition to electronic properties of highly directional covalent bonds, mechanical properties, and also the Debye temperatures of structures support that both are superhard materials. Calculated electronic band structures and density of states revealed that orthorhombic B 28 crystal is a semiconductor, and the tetragonal B 48 is metallic. The pressure-dependent behaviors of both structures are different, and both are ultra-incompressible and anisotropic materials. The physical parameters of the structures such as lattice parameters, bond lengths, and also energy gaps between valance and conduction bands are closely sensitive to applied external pressures. By means of pressure-volume graphs, obtained EOSs for ␣-rhombohedral B 12 , orthorhombic B 28 and tetragonal B 48 boron phases are compared with available data. However, energetically possible pressure-induced phase transitions among the purposed structures are predicted on the pressure range of 0-460 GPa. Furthermore, our calculations showed that for the pressures from 0 GPa to 24 GPa energetically the more stable elemental boron phase is ␣-rhombohedral B 12 , and from 24 GPa to 106 GPa is orthorhombic B 28 , and from 106 GPa to 460 GPa is ␣-Ga-type boron.
High pressure raman study of Bi-2212
High Pressure Research, 2003
The hydrostatic pressure dependence of the Raman spectra of Bi 2 Sr 2 CaCu 2 O 8 single crystals has been investigated. The energy of the A g and B 1g modes was found to increase with pressure in agreement with previously reported measurements, except the strong mode at 465cmAˋ1,whichsoftenswithpressure,whileanotherpeakat465 cm À1 , which softens with pressure, while another peak at 465cmAˋ1,whichsoftenswithpressure,whileanotherpeakat458 cm À1 appears more pronounced at low temperatures and high pressures. The energy of both modes does not seem to change with increasing pressure, up to 5GPa,althoughtheaverageenergyofthewidebandhasbeenfoundtosoften,whichisindisagreementwithpreviouslypublishedresults.Basedonthemodificationsobservedinsomephononsat5 GPa, although the average energy of the wide band has been found to soften, which is in disagreement with previously published results. Based on the modifications observed in some phonons at 5GPa,althoughtheaverageenergyofthewidebandhasbeenfoundtosoften,whichisindisagreementwithpreviouslypublishedresults.Basedonthemodificationsobservedinsomephononsat1.8 GPa, which correlate with the reduction of T c and the deformations of the CuO 5 pyramids, we attribute the mode at $465 cm À1 to the vibrations of the apex oxygen atoms. All modes due to the oxygen atoms were found to be strongly anharmonic.
Raman signatures of pressure induced electronic topological and structural transitions in Bi2Te3
Solid State Communications, 2012
We report Raman signatures of electronic topological transition (ETT) at 3.6 GPa and rhombohedral (α-Bi 2 Te 3 ) to monoclinic (β-Bi 2 Te 3 ) structural transition at ~ 8 GPa. At the onset of ETT, a new Raman mode appears near 107 cm -1 which is dispersionless with pressure. The structural transition at ~ 8 GPa is marked by a change in pressure derivative of A 1g and E g mode frequencies as well as by appearance of new modes near 115 cm -1 and 135 cm -1 . The mode Grüneisen parameters are determined in both the α and β-phases. a) Electronic mail-asood@physics.iisc.ernet.in