We have performed first-principles calculations of the electronic structure ZnO, and applied them to determination structural lattice-dynamical properties their dependence on pressure. The dynamical matrices been obtained for wurtzite, zinc-blende, rocksalt modifications with several lattice parameters optimized pressures up 12 GPa. These are employed calculate one-phonon densities states (DOS) two-phonon DOS associated either sums or differences phonons. results provide essential tools...

Anomalous Raman modes have been reported in several recent papers dealing with doped- and undoped-ZnO layers grown by different methods. Most of these anomalous attributed to local vibrational impurities or defects. However, we will show that most the observed correspond wurtzite-ZnO silent allowed breakdown translational crystal symmetry induced defects impurities.

Angle-dispersive x-ray diffraction (ADXRD) and absorption near edge structure (XANES) measurements have been performed in the AWO4 tungstates CaWO4 SrWO4 under high pressure up to approximately 20 GPa. Similar phase transitions transition pressures observed for both using two techniques studied range. Both materials are found undergo a pressure-induced scheelite-to-fergusonite sufficiently hydrostatic conditions. Our results compared those previously literature supported by ab initio total...

The structural and vibrational properties of bismuth selenide (Bi${}_{2}$Se${}_{3}$) have been studied by means x-ray diffraction Raman scattering measurements up to 20 30 GPa, respectively. complemented with ab initio total-energy lattice dynamics calculations. Our experimental results evidence a phase transition from the low-pressure rhombohedral ($R$-3$m$) (\ensuremath{\alpha}-Bi${}_{2}$Se${}_{3}$) sixfold coordination for Bi monoclinic $C$2/$m$ structure...

We report an experimental and theoretical lattice dynamics study of antimony telluride (Sb${}_{2}$Te${}_{3}$) up to 26 GPa together with a its structural stability under pressure. Raman-active modes the low-pressure rhombohedral (R-3m) phase were observed 7.7 GPa. Changes frequencies linewidths around 3.5 where electronic topological transition was previously found. Raman-mode changes evidence transitions at 7.7, 14.5, 25 The pressure coefficients new phases above 14.5 agree those calculated...

Phonon linewidths can exhibit a large variation when either pressure or isotopic masses are changed. These effects yield detailed information about the mechanisms responsible for and lifetimes, e.g., anharmonicity disorder. We report Raman measurements of linewidth upper ${\mathrm{E}}_{2}$ phonons ZnO crystals with several compositions their dependence on pressure. Changes by factor 12 observed at given temperature. Comparison calculated densities one-phonon states, isotope scattering,...

This letter reports on the pressure dependence of optical absorption edge ZnO in rock-salt phase, up to 20 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films mica have been investigated. Rock-salt is shown be an indirect semiconductor with a band gap 2.45±0.15 eV, whose coefficient very small. At higher photon energies, direct transition observed (4.6 eV at 10 GPa), positive (around 40±3 meV/GPa between 5 19 GPa). These results are interpreted basis first-principles...

We report an experimental and theoretical lattice dynamics study of bismuth telluride (Bi${}_{2}$Te${}_{3}$) up to 23 GPa together with the optical absorption reflection 10 GPa. The indirect bandgap low-pressure rhombohedral (R-3$m$) phase (\ensuremath{\alpha}-Bi${}_{2}$Te${}_{3}$) was observed decrease pressure at a rate \ensuremath{-}6 meV/GPa. In regard dynamics, Raman-active modes \ensuremath{\alpha}-Bi${}_{2}$Te${}_{3}$ were 7.4 dependence their frequency width provides evidence...

Zinc oxide is a key material for optoelectronic applications, whose transport properties are typically dominated by the lattice vibrations. We report here phonon-dispersion relations of wurtzite ZnO at 10 K, as determined using inelastic neutron scattering. The experimental data analyzed with aid ab initio calculations based on density-functional perturbation theory. A complete picture dynamics drawn from present results, thus contributing to understanding mechanical, thermodynamical, and materials.

X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 16 GPa, respectively. Experiments reveal that at 5.3 GPa the onset of a pressure-induced irreversible phase transition from zircon monazite structure. Beyond this pressure, peaks Raman-active modes are measured. The in CeVO4 is distinctive among other rare-earth orthovanadates. We also observed softening external translational Eg internal B2g bending modes. attributed it mechanical...

Raman scattering measurements and lattice-dynamics calculations were performed on magnesium tungstate (MgWO${}_{4}$) under high pressure up to 41 GPa. Experiments carried out a selection of media. The influence nonhydrostaticity the structural properties MgWO${}_{4}$ isomorphic compounds is examined. Under quasihydrostatic conditions, phase transition was found at 26 GPa in MgWO${}_{4}$. high-pressure tentatively assigned triclinic structure similar that CuWO${}_{4}$. We also report discuss...

Abstract Bi 2 Se 3 , Te and Sb are narrow bandgap semiconductors with tetradymite crystal structure (R‐3m) which have been extensively studied along their alloys due to promising operation as thermoelectric materials in the temperature range between 300 500 K. Studies on these layered increased tremendously last years since they recently predicted demonstrated behave 3D topological insulators. In particular, a number of high‐pressure studies done recent materials. this work we summarize main...

Antimony trisulfide (Sb2S3), found in nature as the mineral stibnite, has been studied under compression at room temperature from a joint experimental and theoretical perspective. X-ray diffraction Raman scattering measurements are complemented with ab initio total-energy, lattice-dynamics, electronic structure calculations. The continuous changes observed volume, lattice parameters, axial ratios, bond lengths, mode frequencies function of pressure can be attributed to different...

We report an experimental and theoretical study of antimony oxide (Sb${}_{2}$O${}_{3}$) in its cubic phase (senarmontite) under high pressure. X-ray diffraction Raman scattering measurements up to 18 25 GPa, respectively, have been complemented with ab initio total-energy lattice-dynamics calculations. do not provide evidence a space-group symmetry change senarmontite GPa. However, changes the pressure coefficients mode frequencies at 3.5 10 respectively. The behavior modes increasing GPa is...

This paper makes use of a smartphone's ambient light sensor to analyze system two coupled springs undergoing either simple or damped oscillatory motion.Period, frequency, stiffness the spring, damping constant, and extinction time are extracted from intensity curves obtained using free Android application.The results demonstrate instructional value mobile phone sensors as tool in physics laboratory.

In this work we report the metastability and energetics of phase transitions three different polymorphs BiPO4, namely trigonal (Phase-I, space group P3121), monoclinic monazite-type (Phase-II, P21/n) SbPO4-type (Phase-III, P21/m) from ambient non-ambient temperature powder XRD neutron diffraction studies as well ab initio density functional theory (DFT) calculations. The symmetry ambiguity between P21 P21/m high polymorph BiPO4 has been resolved by a study. structure vibrational properties...

In this work, we report evidence of pressure-induced changes in the crystal structure Sr(IO3)2HIO3 connected to coordination iodine atom and configuration HIO3 IO3 units. The favor hypercoordination happen two steps on sample compression. Firstly, at 2.5 GPa, [HIO3]·[IO3] complexes are formed, secondly, 4.5 these form dimers [HIO3]·[IO3]·[IO3]·[HIO3]. is obtained from a combined experimental theoretical study performed up 20 GPa. Synchrotron powder X-ray diffraction, Raman spectroscopy,...

We report the results of both angle-dispersive x-ray diffraction and absorption near-edge structure studies in $\mathrm{Ba}\mathrm{W}{\mathrm{O}}_{4}$ $\mathrm{Pb}\mathrm{W}{\mathrm{O}}_{4}$ at pressures up to $56\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ $24\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, respectively. is found undergo a pressure-driven phase transition $7.1\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ from tetragonal scheelite (which stable under normal conditions) monoclinic...

Room-temperature Raman scattering has been measured in barium tungstate $(\mathrm{Ba}\mathrm{W}{\mathrm{O}}_{4})$ up to $16\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. We report the pressure dependence of all active first-order phonons tetragonal scheelite phase ($\mathrm{Ba}\mathrm{W}{\mathrm{O}}_{4}\text{\ensuremath{-}}I$, space group $I{4}_{1}∕a$), which is stable at normal conditions. As increases spectrum undergoes significant changes around $6.9\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ due...

A nonlinear optical effect is shown to occur in gallium and indium selenides at photon energies of the order 1.5 eV. It corresponds transitions from a lower-energy valence band uppermost one when nonequilibrium degenerate hole gas created latter by laser pulse. This inter-valence-band transition allowed crystal symmetry. Its oscillator strength estimated through $f$-sum rule turns out be about two orders magnitude higher than that fundamental transition. The intensity this stronger pump...

Room temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, undergoes a transition from the cubic structure tetragonal similar that ZnMn2O4. 55 second orthorhombic marokite (CaMn2O4-type) takes place. The equation state is determined: V0 = 580.1(9) A3, B0 233(8) B0'= 8.3(4), and B0''= -0.1145 GPa-1 (implied value); showing one less compressible spinels studied date. For an also 257.8(9)...

The room-temperature Raman scattering was measured in ${\text{ZnWO}}_{4}$ up to 45 GPa. We report the pressure dependence of all Raman-active phonons low-pressure wolframite phase. As increases additional peaks appear at 30.6 GPa due onset a reversible structural phase transition distorted monoclinic $\ensuremath{\beta}$-fergusonite-type and high-pressure phases coexist from 36.5 In addition measurements we also ab initio total-energy lattice-dynamics calculations for two phases. These...