scholarly journals Динамика решеток и барическое поведение фононов в модельных сегнетоэластиках Hg-=SUB=-2-=/SUB=-Br-=SUB=-2-=/SUB=-

2019 ◽  
Vol 61 (2) ◽  
pp. 325
Author(s):  
Е.М. Рогинский ◽  
А.С. Крылов ◽  
Ю.Ф. Марков
Keyword(s):  
Brillouin Zone ◽  
Tetragonal Phase ◽  
High Pressures ◽  
Soft Mode ◽  
Anomalous Behavior ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Wide Range ◽  
Phase Spectra ◽  
High Hydrostatic Pressures

AbstractRaman spectra of Hg_2Br_2 model improper ferroelastic crystals have been investigated in a wide range of high hydrostatic pressures. Baric dependences of the phonon frequencies have been obtained; of greatest interest are the observed soft mode originating from the slowest TA _1 acoustic branch at the Brillouin zone boundary ( X point) of the tetragonal phase and the anomalous behavior of this mode. In the ferroelastic phase spectra, the ignition of the second acoustic TA _2 from the same point has also been detected and its baric behavior has been studied. Under sufficiently high pressures, splitting of doubly degenerate phonons with the E _ g symmetry has been observed and explained. The parameters of the Grüneisen constants have been determined from the baric dependences of the phonon frequencies and discussed.

scholarly journals Эффекты фазового перехода, индуцированные давлением, в модельных сегнетоэластиках Hg-=SUB=-2-=/SUB=-Br-=SUB=-2-=/SUB=-

2018 ◽  
Vol 44 (17) ◽  
pp. 3
Author(s):  
Е.М. Рогинский ◽  
А.С. Крылов ◽  
Ю.Ф. Марков
Keyword(s):  
Tetragonal Phase ◽  
Boundary Point ◽  
Acoustic Phonon ◽  
High Pressures ◽  
Soft Mode ◽  
Anomalous Behavior ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Wide Range ◽  
Phase Spectra

AbstractRaman spectra of model improper ferroelastics (Hg_2Br_2 crystals) have been analyzed in a wide range of hydrostatic pressures. The baric dependences of the phonon frequencies are obtained. The revealing and anomalous behavior of the soft mode, which is genetically related to the acoustic phonon (ТА_1) at the Brillouin zone boundary (point X ) of the tetragonal phase, are most interesting. The buildup of the second acoustic phonon (ТА_2) from the same point has also been found in the ferroelastic-phase spectra, and its baric behavior has been investigated. The splitting of doubly degenerate phonons of the E _g symmetry has been revealed at fairly high pressures and explained.

Angular control of acoustic waves oblique incidence by phononic crystals based on Dirac cones at the Brillouin zone boundary

2018 ◽  
Vol 382 (6) ◽  
pp. 423-427 ◽  
Author(s):  
Wen-Qiang Zhang ◽  
Xin Zhang ◽  
Fu-Gen Wu ◽  
Yuan-Wei Yao ◽  
Shui-Fang Lu ◽  
...  
Keyword(s):  
Brillouin Zone ◽  
Acoustic Waves ◽  
Oblique Incidence ◽  
Phononic Crystals ◽  
Zone Boundary ◽  
Brillouin Zone Boundary

Photonic Band Structure of Nanochannel Glass Materials

1996 ◽  
Vol 431 ◽  
Author(s):  
A. Rosenberg ◽  
R. J. Tonucci ◽  
H.-B. Lin
Keyword(s):  
Band Structure ◽  
Brillouin Zone ◽  
Near Infrared ◽  
Nearest Neighbor ◽  
Dielectric Structure ◽  
Zone Boundary ◽  
Photonic Band Structure ◽  
Brillouin Zone Boundary ◽  
Photonic Band ◽  
Good Agreement

AbstractWe demonstrate that nanochannel glass (NCG) materials are ideal for investigating twodimensional (2D) photonic band-structure effects. The NCG materials we have studied consist of triangular arrays of glass cylinders embedded in a glass matrix, having center-tocenter nearest-neighbor separations from 0.54 to 1.08 μm. The indices of refraction of the two glasses differ by less than 0.02 in the relevant spectral region. Narrow attenuation features occur whenever the dispersion relation for light propagating within such a periodic dielectric structure crosses a Brillouin zone boundary. The attenuations corresponding to the first Brillouin zone appear in the near-infrared (IR), at wavelengths between 1 and 3 μm, in good agreement with calculations.

Tilt and acoustic instabilities in ABX 4, A 2 BX 4 and ABX 3 perovskite structure types: their role in the incommensurate phases of the organic–inorganic perovskites

2005 ◽  
Vol 61 (6) ◽  
pp. 616-626 ◽  
Author(s):  
Ian Peter Swainson
Keyword(s):  
Brillouin Zone ◽  
Three Dimensional ◽  
Low Frequency ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Perovskite Layer ◽  
Modulated Phases ◽  
Acoustic Instabilities ◽  
Incommensurate Phases ◽  
Zero Frequency

An examination of the tilt modes and other low-frequency modes is made for an isolated, untilted perovskite layer, which maps very simply to the ABX 4 perovskites. A sheet of pure tilts exists at the Brillouin Zone boundary at {ξ, ½, ζ}. An instability is also found at all wavevectors which can be described as continuously varying from pure tilts to pure layer displacements as a function of the wavevector. Analysis is extended by considering the stacking of layers in the I-centered A 2 BX 4-layer perovskites. The effect of freezing in the commensurate tilt required to generate the Cmca tilt system, pertinent to the modulated phases of propylammonium salts, is examined. The zero-frequency modes are restricted to two planes in the Brillouin Zone. All of the observed wavevectors associated with modulated phases, and the commensurately tilted propylammonium tetrachlorocadmate, are consistent with this calculation. The effect of full three-dimensional connectivity is briefly reviewed for the true ABX 3 perovskites. While pure tilt incommensurates appear to be hypothetically possible, they do not appear to have been observed to date.

scholarly journals Nodal Brillouin-zone boundary from folding a Chern insulator

2017 ◽  
Vol 95 (5) ◽  
Author(s):  
Li-Jun Lang ◽  
Shao-Liang Zhang ◽  
Qi Zhou
Keyword(s):  
Brillouin Zone ◽  
Zone Boundary ◽  
Brillouin Zone Boundary

Magnetic excitations at the Brillouin zone boundary in Mn (17%Fe, 3%Cu) alloy

2004 ◽  
Vol 350 (1-3) ◽  
pp. E79-E81
Author(s):  
J Jankowska-Kisielińska ◽  
K Mikke ◽  
B Hennion
Keyword(s):  
Brillouin Zone ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Magnetic Excitations ◽  
Cu Alloy
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