Showing papers on "Brillouin zone published in 2004"
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TL;DR: In this article, a scheme for the calculation of linear optical properties by the all-electron full-potential linearized augmented planewave (LAPW) method is presented.
Abstract: We present a scheme for the calculation of linear optical properties by the all-electron full-potential linearized augmented planewave (LAPW) method. A summary of the theoretical background for the derivation of the dielectric tensor within the random-phase approximation is provided together with symmetry considerations and the relation between the optical constants. The momentum matrix elements are evaluated in detail for the LAPW basis, and the interband as well as the intraband contributions to the dielectric tensor are given. Results are presented for the metals aluminum and gold, where we crosscheck our results by sumrules. We find that the optical spectra can be extremely sensitive to the Brillouin zone sampling. For gold, the influence of relativistic effects on the dielectic function is investigated. It is shown that the scalar-relativistic effect is much more important than spin-orbit coupling. The interpretability of the Kohn-Sham eigenstates in terms of excited states is discussed.
815 citations
TL;DR: The first experimental observation of bright matter wavesolitons for 87Rb atoms with repulsive atom-atom interaction is reported, allowing the systematic investigation of gap solitons.
Abstract: We report on the first experimental observation of bright matter wave solitons for $^{87}\mathrm{Rb}$ atoms with repulsive atom-atom interaction. This counterintuitive situation arises inside a weak periodic potential, where anomalous dispersion can be realized at the Brillouin zone boundary. If the coherent atomic wave packet is prepared at the corresponding band edge, a bright soliton is formed inside the gap. The strength of our system is the precise control of preparation and real time manipulation, allowing the systematic investigation of gap solitons.
550 citations
TL;DR: In this paper, the spin-orbit interaction leads to a strong splitting of the surface-state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone.
Abstract: Using first-principles calculations and angle-resolved photoemission, we show that the spin-orbit interaction leads to a strong splitting of the surface-state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone. We discuss the implications of these findings with respect to a proposed surface charge density wave on Bi(111) as well as to the surface screening, surface spin-density waves, electron (hole) dynamics in surface states, and to possible applications to the spintronics.
488 citations
TL;DR: In this paper, the authors measured the dispersion of graphite optical phonons in the in-plane Brillouin zone by inelastic x-ray scattering and showed that first-principles calculations describe very well the vibrational properties of graphene once the long-range character of the dynamical matrix is taken into account.
Abstract: We measured the dispersion of the graphite optical phonons in the in-plane Brillouin zone by inelastic x-ray scattering. The longitudinal and transverse optical branches cross along the � -K as well as the � -M direction. The dispersion of the optical phonons was, in general, stronger than expected from the literature. At the K point the transverse optical mode has a minimum and is only � 70 cm � 1 higher in frequency than the longitudinal mode. We show that first-principles calculations describe very well the vibrational properties of graphene once the long-range character of the dynamical matrix is taken into account.
437 citations
TL;DR: In this article, a waveguide with vanishing second-and third-order dispersion is presented, which can be explained by the strong interaction of the modes with the bulk photonic crystal waveguide.
Abstract: Modes of photonic crystal (PC) line-defect waveguides can have small group velocity away from the Brillouin zone edge. This property can be explained by the strong interaction of the modes with the bulk PC. An anticrossing of “index guided” and “gap guided” modes should be taken into account. To control dispersion, the anticrossing point can be shifted by the change of the PC waveguide parameters. An example of a waveguide is presented with vanishing second- and third-order dispersion.
269 citations
TL;DR: In this article, the authors present a comprehensive analysis of double-resonant Raman scattering in graphite and derive an analytical expression for the Raman cross section of the D mode in one dimension.
Abstract: We present a comprehensive analysis of double-resonant Raman scattering in graphite and derive an analytical expression for the Raman cross section of the D mode in one dimension. The extension to two dimensions does not change the double-resonant phonon wave vectors. In the full integration of the Raman cross section, the contributions by phonons from exactly the K point cancel due to destructive interference. We calculate the D mode explicitly based on recent experimental data of the graphite phonon dispersion. Applying the selection rules, a mapping of additional disorder-induced and second-order Raman modes onto the Brillouin zone of graphite is obtained. DOI: 10.1103/PhysRevB.70.155403
263 citations
TL;DR: In this paper, the authors presented an accurate numerical simulation of the Brillouin gain spectrum (BGS) in single-mode fibers and revealed a tendency of the peak BGS gain coefficient that determines the stimulated BrillouIN scattering threshold.
Abstract: For many fiber applications, the Brillouin gain spectrum (BGS) contains important information including the Brillouin frequency shift, the Brillouin spontaneous linewidth, and the Brillouin gain coefficient. This paper is the first, to the best of our knowledge, to present an accurate numerical simulation of the BGS in single-mode fibers. The simulated and measured BGS were in good agreement. Through repeated numerical simulations, we revealed a tendency of the peak Brillouin gain coefficient that determines the stimulated Brillouin scattering threshold.
235 citations
TL;DR: In this paper, the authors performed ab initio calculations of the optical absorption spectrum and the wavevector-dependent dielectric and energy-loss functions of graphite in the framework of the random-phase approximation.
Abstract: We performed ab initio calculations of the optical absorption spectrum and the wave-vector-dependent dielectric and energy-loss functions of graphite in the framework of the random-phase approximation. In the absorption spectrum, the most prominent peaks were analyzed in terms of interband transitions from specific regions of the Brillouin zone. The inclusion of the crystal local-field effects (LFE) in the response had an important influence on the absorption spectrum for light polarization parallel to the c axis. The calculated electron energy-loss spectra, even without LFE, were in very good agreement with existing momentumdependent energy-loss experiments concerning the peak positions of the two valence-electron plasmons. Important aspects of the line shape and anisotropy of the energy-loss function at large momentum transfer q were also well described: the splitting of the total sp +sd plasmon and the appearance of peaks originating from interband transitions. Finally, the role of the interlayer interaction was studied, in particular with regard to its effect on the absorption spectrum for light polarization parallel to c, and to the position of the higher-frequency p +s plasmon.
172 citations
TL;DR: The AO-based t1 amplitudes appear to correlate strongly with the electronic structure, and they decay seemingly exponentially for polyethylene whereas they stay at a constant magnitude across the seventh nearest neighbors of polyacetylene and polyyne, which attests to far reaching effects of nondynamical electron correlation mediated by orbital rotation.
Abstract: Coupled-cluster theory with connected single and double excitation operators (CCSD) and related approximations, such as linearized CCSD, quadratic configuration interaction with single and double excitation operators, coupled-cluster with connected double excitation operator (CCD), linearized CCD, approximate CCD, and second- and third-order many-body perturbation theories, are formulated and implemented for infinitely extended one-dimensional systems (polymers), on the basis of the periodic boundary conditions and distance-based screening of integrals, density matrix elements, and excitation amplitudes. The variation of correlation energies with the truncation radii of short- and long-range lattice sums and with the number of wave vector sampling points in the first Brillouin zone is examined for polyethylene, polyacetylene, and polyyne, and is shown to be a function of the degree of π-electron conjugation or the fundamental band gaps. The t2 and t1 amplitudes in the atomic orbital (AO) basis are obtaine...
152 citations
TL;DR: In this paper, the authors studied the energy transport in chains of noncontacting metal nanoparticles within an exactly solvable model, where the transport is mediated by the electromagnetic interactions between plasmons confined to the individual nanoparticles.
Abstract: Electromagnetic energy transport in chains of noncontacting metal nanoparticles is studied within an exactly solvable model. The transport is mediated by the retarded electromagnetic interactions between plasmons confined to the individual nanoparticles and therefore self-consistently accounts for spontaneous emission on the same footing as the transport; the propagating hybrid plasmonic-electromagnetic modes of the chain are known as plasmon polaritons. Dark modes are found in the first Brillouin zone when the excitation wavelength is greater than the resonant optical wavelength, suggesting the possibility of the suppression of radiative losses. Nearest-neighbor tight-binding models are shown to be of limited validity.
139 citations
TL;DR: The feasibility of the highly precise simultaneous measurement of temperature and strain by use of the PCF in a distributed Brillouin sensing system with a spatial resolution of 15 cm is demonstrated.
Abstract: The dependence of the Brillouin frequency shift on strain in a photonic crystal fiber (PCF) was measured at a wavelength of 1320 nm for the first time to the authors’ knowledge. Together with measurements of the dependence of the Brillouin frequency shift on temperature in the PCF, we demonstrate the feasibility of the highly precise simultaneous measurement of temperature and strain by use of the PCF in a distributed Brillouin sensing system with a spatial resolution of 15 cm.
TL;DR: In this article, the Mott transition was investigated using a cluster extension of dynamical mean field theory (DMFT), and no evidence for a finite temperature Mott critical point was found.
Abstract: We investigate the Mott transition using a cluster extension of dynamical mean field theory (DMFT). In the absence of frustration we find no evidence for a finite temperature Mott transition. Instead, in a frustrated model, we observe signatures of a finite temperature Mott critical point in agreement with experimental studies of $\ensuremath{\kappa}$ organics and with single-site DMFT. As the Mott transition is approached, a clear momentum dependence of the electron lifetime develops on the Fermi surface with the formation of cold regions along the diagonal direction of the Brillouin zone. Furthermore, the variation of the effective mass is no longer equal to the inverse of the quasiparticle residue, as in DMFT, and is reduced approaching the Mott transition.
TL;DR: In this article, the effects of absorption losses in photonic crystal structures composed of polar materials which exhibit transverse phonon-polariton excitations were examined, and two subspaces of the complete set of complex (k,v) states consisting of either real frequency, accessible through a frequency-domain method, or real-wave vector, which were determined using a frequencydependent time-domain approach.
Abstract: We examine the effects of absorption losses in photonic crystal structures composed of polar materials which exhibit transverse phonon-polariton excitations. In order to explore the Bloch states of such a system, we study the two subspaces of the complete set of complex (k ,v) states consisting of either real frequency, accessible through a frequency-domain method, or real-wave vector, which we determine using a frequency-dependent time-domain method. We describe analytically the conditions under which the imaginary frequency component of a real-wave-vector state is related to the imaginary-wave-vector component of a real-frequency state through a factor of the group velocity, and we present a one-dimensional lossy crystal as an example that satisfies these constraints. We also discover that the real-frequency states of a two-dimensional crystal bear little resemblance to the class of real-wave-vector states, due to interplay between the prohibitively large spatial decay of the states near the edge of the Brillouin zone and the existence of metalliclike states localized to the surrounding ambient dielectric region with much lower levels of loss. We then put these results in the context of possible experiments, including reflection of a plane-wave from a slab structure, and discuss the viability for observing the node switching and flux expulsion phenomena previously discovered in lossless crystals.
TL;DR: In this article, a modified Monkhorst-Pack (MMP) special points meshes for cubic crystals are proposed for Brillouin zone integration, which ensure the higher precision of the points summation and faster and regular convergence of the results of the self-consistent calculations of the electronic structure of crystals.
Abstract: Modified Monkhorst-Pack (MMP) special points meshes for Brillouin zone integration are proposed for cubic crystals. The MMP meshes suggested ensure the higher precision of $\mathbf{k}$-points summation and faster and regular convergence of the results of the self-consistent calculations of the electronic structure of crystals. The efficiency of MMP meshes is demonstrated by DFT-GGA (density functional theory - generalized gradient corrections) calculations of $\mathrm{SiC}$ crystal.
TL;DR: A detailed experimental study of the optical properties in the high-energy region (up to $a∕\ensuremath{\lambda}=1.8$) of high-quality artificial opals is performed by means of reflection and transmission spectroscopy as discussed by the authors.
Abstract: A detailed experimental study of the optical properties in the high-energy region (up to $a∕\ensuremath{\lambda}=1.8$) of high-quality artificial opals is performed by means of reflection and transmission spectroscopy. A number of issues, such as scalability and finite size effects, are taken into account before tentative comparison with theory is carried out. The experimental system under study is further modified by a controlled filling of the interstitials between the spheres, and its optical properties monitored throughout the process. We observe that the main features of the optical response of artificial opals seem to be accounted for by bands originated by wave vectors parallel to the $\ensuremath{\Gamma}L$ direction and their perturbations, such as gaps opening at the center and edges of the Brillouin zone and anticrossings elsewhere, introduced through the interaction with other bands of similar energy and symmetry. This work constitutes an experimental approach to understand the interaction of light with photonic bands which introduces a challenge for future experimental and theoretical work.
TL;DR: A recently proposed method of measuring the two Brillouin frequencies in a multicompositional fiber core for unambiguously resolving temperature and strain in a distributed sensor is compared with the previously established technique of measure the intensity and frequency of the single BrillouIn peak in a standard single-mode fiber.
Abstract: A recently proposed method of measuring the two Brillouin frequencies in a multicompositional fiber core for unambiguously resolving temperature and strain in a distributed sensor is compared with the previously established technique of measuring the intensity and frequency of the single Brillouin peak in a standard single-mode fiber
TL;DR: In this article, the magnetic field dependences of the frequencies of standing spinwave modes in a tangentially magnetized array of thin rectangular permalloy dots (800 × 550 nm) were measured experimentally by a Brillouin light scattering technique and calculated theoretically using an approximate size-dependent quantization of the spin-wavevector components in the dipole-exchange dispersion equation for spin waves propagating in a continuous magnetic film.
Abstract: The magnetic field dependences of the frequencies of standing spin-wave modes in a tangentially magnetized array of thin rectangular permalloy dots (800 × 550 nm) were measured experimentally by a Brillouin light scattering technique and calculated theoretically using an approximate size-dependent quantization of the spin-wavevector components in the dipole-exchange dispersion equation for spin waves propagating in a continuous magnetic film. It was found that the inhomogeneous internal bias magnetic field of the dot has a strong influence on the profiles of the lowest spin-wave standing modes. In addition, the dynamic magnetization distributions found for both longitudinally and transversely magnetized long magnetic stripes gives a good approximation for mode distributions in a rectangular dot magnetized along one of its in-plane sides. An approximate analytic theory of exchange-dominated spin-wave modes, strongly localized along the dot edge that is perpendicular to the bias magnetic field, is developed. A good quantitative agreement with the results of the BLS experiment is found.
TL;DR: In this article, isothermal compressibilities and Brillouin sound velocities from the literature were used to separate the compressibility at the glass transition into a high-frequency vibrational and a low-frequency relaxational part.
Abstract: Isothermal compressibilities and Brillouin sound velocities from the literature allow us to separate the compressibility at the glass transition into a high-frequency vibrational and a low-frequency relaxational part. Their ratio shows the linear fragility relation discovered by x-ray Brillouin scattering, though the data bend away from the line at higher fragilities. Using the concept of constrained degrees of freedom, one can show that the vibrational part follows the fragility-independent Lindemann criterion; the fragility dependence seems to stem from the relaxational part. The physical meaning of this finding is discussed.
TL;DR: In this paper, a structural phase transition from orthorhombic α-SnS to monoclinic γ-snS was observed at 18.15 GPa and the improper ferro-elastic transition is accompanied by a large volume discontinuity of about 9.1%.
Abstract: The structural behaviour of SnS under high-pressure has been investigated by angular dispersive synchrotron powder diffraction up to 38.5 GPa. A structural phase transition from orthorhombic α-SnS to monoclinic γ-SnS was observed at 18.15 GPa. The fit of a Birch–Murnaghan equation-of-state gave the volume at zero pressure of V0 = 192.6(3) A3, the bulk modulus at zero pressure of B0 = 36.6(9) GPa and the pressure derivative of the bulk modulus for α-SnS and V0 = 160(1) A, B0 = 86.0(5) GPa and for γ-SnS. The improper ferro-elastic transition is of first-order and is accompanied by a large volume discontinuity of about 9.1%. The phase transition can be described in terms of a group/subgroup relationship. The doubling of the unit cell indicates a wavevector (1/2,0,1/2) at the U-point in the Brillouin zone.
TL;DR: In this paper, the optical properties associated with photonic bands of three-dimensional photonic colloidal crystals are analyzed in terms of the band structure of the crystal and a relationship is found between dispersion of the bands and the features observed experimentally.
Abstract: Here we report on the optical properties associated with photonic bands of three-dimensional photonic colloidal crystals. Optical spectroscopy analysis shows fluctuations of the transmitted and reflected light intensity in photon frequency regions where no stop bands open up. The different optical features observed at low and high photon energy ranges are analyzed in terms of the band structure of the crystal. A relationship is found between dispersion of the bands and the features observed experimentally. On these premises, we show it is possible to map the higher-energy band region along nonprincipal directions of the first Brillouin zone by transmission spectroscopy.
TL;DR: In this article, the dynamics of nonlinear localized excitations ('solitons') in two-dimensional (2D) Bose?Einstein condensates (BECs) with repulsive interactions, loaded into an optical lattice (OL), was combined with an external parabolic potential.
Abstract: We study the dynamics of nonlinear localized excitations ('solitons') in two-dimensional (2D) Bose?Einstein condensates (BECs) with repulsive interactions, loaded into an optical lattice (OL), which is combined with an external parabolic potential First, we demonstrate analytically that a broad ('loosely bound', LB) soliton state, based on a 2D Bloch function near the edge of the Brillouin zone (BZ), has a negative effective mass (while the mass of a localized state is positive near the BZ centre) The negative-mass soliton cannot be held by the usual trap, but it is safely confined by an inverted parabolic potential (anti-trap) Direct simulations demonstrate that the LB solitons (including those with intrinsic vorticity) are stable and can freely move on top of the OL The frequency of the elliptic motion of the LB-soliton's centre in the anti-trapping potential is very close to the analytical prediction which treats the solition as a quasi-particle In addition, the LB soliton of the vortex type features real rotation around its centre We also find an abrupt transition, which occurs with the increase of the number of atoms, from the negative-mass LB states to tightly bound (TB) solitons An estimate demonstrates that for the zero-vorticity states, the transition occurs when the number of atoms attains a critical number Ncr ~ 103, while for the vortex the transition takes place at Ncr ~ 5 ? 103 atoms The positive-mass LB states constructed near the BZ centre (including vortices) can also move freely The effects predicted for BECs also apply to optical spatial solitons in bulk photonic crystals
TL;DR: In this paper, a (11 2 0 ) a -plane InN film grown by molecular beam epitaxy on ( 1 1 02 ) r -plane sapphire substrate with an AlN nucleation layer and a GaN buffer was studied by spectroscopic ellipsometry.
TL;DR: In this paper, a generalized force constant model is used to interpolate throughout the Brillouin zone and evaluate moments of the phonon distribution, which are used to calculate the volume dependence of the Gruneisen parameter in the fcc solid.
Abstract: Elastic constants and zone-boundary phonon frequencies of gold are calculated by total energy electronic structure methods to twofold compression A generalized force constant model is used to interpolate throughout the Brillouin zone and evaluate moments of the phonon distribution The moments are used to calculate the volume dependence of the Gr\"uneisen parameter in the fcc solid Using these results with ultrasonic and shock data, we formulate the complete free energy for solid Au This free energy is given as a set of closed-form expressions, which are valid to compressions of at least ${V/V}_{0}=065$ and temperatures up to melting Beyond this density, the Hugoniot enters the solid-liquid mixed phase region Effects of shock melting on the Hugoniot are discussed within an approximate model We compare with proposed standards for the equation of state to pressures of $\ensuremath{\sim}200\mathrm{GPa}$ Our result for the room-temperature isotherm is in very good agreement with an earlier standard of Heinz and Jeanloz
TL;DR: In this paper, the electronic energy band structures and total density of states (DOS) of BaTiO 3 (Barium strontium titanate, BST) were calculated by the first-principles method using density-functional theory in its local density approximation.
Abstract: The electronic-energy band structures and total density of states (DOS) of Sr-substituted BaTiO 3 (Barium strontium titanate, BST) are calculated by the first-principles method using density-functional theory in its local-density approximation. The calculated band structure shows a direct band gap of 1.96 eV at the Γ point in the Brillouin zone. The optical spectra of the perovskites in the photon energy range up to 30 eV are investigated by the first-principles under the scissor approximation. The real and imaginary parts of the dielectric function and thus the optical constants, i.e. the refractive index, extinction coefficient are calculated. The calculated spectra are compared with the experimental results for BaTiO 3 , SrTiO 3 at room temperature and are found to be in good agreement with the experimental data.
TL;DR: This work accelerates a Bose-Einstein condensate in a controlled way across the edge of the Brillouin zone of a 1D optical lattice and describes the onset of instability as the acceleration of the lattice is decreased.
Abstract: By accelerating a Bose-Einstein condensate in a controlled way across the edge of the Brillouin zone of a 1D optical lattice, we investigate the stability of the condensate in the vicinity of the zone edge. Through an analysis of the visibility of the interference pattern after a time-of-flight and the widths of the interference peaks, we characterize the onset of instability as the acceleration of the lattice is decreased. We briefly discuss the significance of our results with respect to recent theoretical work.
TL;DR: In this article, the lattice dynamical properties of novel semiconductor InN thin films are reviewed and some prospects on Raman scattering studies in the related materials and structures are presented.
Abstract: We review recent experimental studies on the lattice dynamical properties of novel semiconductor InN thin films. Most of the experimental results are concerned with Raman scattering as well as infrared spectroscopic studies. The emphasis is on the structure of Brillouin zone centre (? point) phonons in InN (including both the wurtzite and zinc blende structures), coupling between the electron excitation (plasmon) and the longitudinal optical phonon, disorder-activated modes, temperature-?and pressure-dependences of the lattice vibration modes, micro-Raman imaging, and the lattice vibration in nitride alloys, superlattices, quantum wells, and quantum dots, etc. This article also presents some prospects on Raman scattering studies in the related materials and structures.
TL;DR: In this article, the effect of the mixing of Eu f states with B p states around the X point of the Brillouin zone has been studied and it is shown that the effect on the effective exchange between the itinerant electrons and the local $4f$ moments has been investigated.
Abstract: With a treatment of the $4f$ states of ${\mathrm{EuB}}_{6}$ based on $\mathrm{LDA}+U$ (LDA---local-density approximation) method, the mixing of Eu f states with B p states around the X point of the Brillouin zone is shown to have unexpected consequences for the effective exchange interactions. We analyze in detail the orbital character of electronic states close to the Fermi level and discuss the effective exchange between the itinerant electrons and the local $4f$ moments. The analysis suggests that the ordered phase may provide the first example of a half-metallic semimetal, and that the physics of ${\mathrm{EuB}}_{6}$ should be described in terms of a two-band Kondo lattice model with parallel (ferromagnetic) coupling of the conduction electrons and antiparallel (antiferromagnetic) coupling of the valence electrons to the local $4f$ moments.
TL;DR: In this article, angular-resolved photoemission investigations of the Shockley-type surface state on the reconstructed (111) surface of gold were performed, where the so-called herringbone reconstruction, with three different 22×31/2 domain orientations, formed a superlattice that has a clearly observable influence on the surface electronic structure.
Abstract: We present angular-resolved photoemission investigations of the Shockley-type surface state on the reconstructed (111) surface of gold. The so-called herringbone reconstruction, with three different 22×31/2domain orientations, forms a super-lattice that has a clearly observable influence on the surface electronic structure. In the L gap of the projected bulk states, there appears a non-uniform photoemission intensity distribution due to the back-folding of the Shockley state at the Bragg planes of the reduced surface Brillouin zone. Furthermore, there is a clear indication of the existence of surface-state band gaps in the electronic density of states of the Shockley state.
TL;DR: By numerical simulations it is shown that the modulationally unstable solutions lead to the formation of localized ground states of the coupled BEC system.
Abstract: Coupled nonlinear Schroedinger (CNLS) equations with an external elliptic function potential model with high accuracy a quasi-one-dimensional interacting two-component Bose-Einstein condensate (BEC) trapped in a standing wave generated by a few laser beams. The construction of stationary solutions of the two-component CNLS equation with a periodic potential is detailed and their stability properties are studied by direct numerical simulations. Some of these solutions allow reduction to the Manakov system. From a physical point of view the trivial phase solutions can be interpreted as exact Bloch states at the edge of the Brillouin zone. Some of them are stable while others are found to be unstable against weak modulations of long wavelength. By numerical simulations it is shown that the modulationally unstable solutions lead to the formation of localized ground states of the coupled BEC system.
TL;DR: In this paper, the dynamics of a soft sphere model glass, studied by molecular dynamics, is investigated and the vibrational density of states divided by ω2 shows a pronounced boson peak.
Abstract: The dynamics of a soft sphere model glass, studied by molecular dynamics, is investigated. The vibrational density of states divided by ω2 shows a pronounced boson peak. Its shape is in agreement with the universal form derived for soft oscillators interacting with sound waves. The excess vibrations forming the boson peak have mainly transverse character. From the dynamic structure factor in the Brillouin regime pseudo dispersion curves are calculated. Whereas the longitudinal phonons are well defined up to the pseudo zone boundary the transverse ones rapidly get over-damped and go through the Ioffe–Regel limit near the boson peak frequency. In the high q regime constant-ω scans of the dynamic structure factor for frequencies around the boson peak are clearly distinct from those for zone boundary frequencies. Above the Brillouin regime, the scans for the low frequency modes follow closely the static structure factor. This still holds after a deconvolution of the exact harmonic eigenmodes into local and extended modes. Also the structure factor for local relaxations at finite temperatures resembles the static one. This semblance between the structure factors mirrors the collective motion of chain-like structures in both low frequency vibrations and atomic hopping processes, observed in the earlier investigations.