Group Theoretical Analysis of Lattice Vibrations in GaSe Polytypes

1974 ◽  
Vol 52 (24) ◽  
pp. 2454-2458 ◽  
Author(s):  
S. Jandl ◽  
J. L. Brebner
Keyword(s):  
Theoretical Analysis ◽  
Raman Scattering ◽  
Brillouin Zone ◽  
Wave Vector ◽  
Lattice Vibrations ◽  
Group Theoretical Analysis

We present here a group theoretical analysis of the lattice vibrations of the ε and γ polytypes of GaSe for different directions of the wave vector in the Brillouin zone. The effect of the interlayer interactions and the assignment of the modes observed in Raman scattering is discussed.

Gitterschwingungsspektren. XV. FIR-Spektren und Schwingungsanalyse von FeS2-Markasit / Lattice Vibration Spectra. XV. FIR-Spectra and Vibration Analysis of FeS2 Marcasite

1975 ◽  
Vol 30 (11) ◽  
pp. 1458-1461
Author(s):  
H. D. Lutz ◽  
P. Willich
Keyword(s):  
Theoretical Analysis ◽  
Vibration Analysis ◽  
Lattice Vibration ◽  
Normal Incidence ◽  
Vibrational Modes ◽  
Lattice Vibrations ◽  
Vibration Spectra ◽  
Symmetry Coordinates ◽  
Fir Spectra ◽  
Group Theoretical Analysis

The infrared-active lattice vibrations of the orthorombic marcasite (FeS2) have been studied by measuring the reflectivity of different crystal faces at near-normal incidence. A group-theoretical analysis predicts seven infrared-active modes (k = 0). Cartesian symmetry coordinates as well as vibrational modes of the lattice vibrations are constructed

scholarly journals Антиферродисторсионная мягкая мода в кристалле PbZr-=SUB=-0.024-=/SUB=-Ti-=SUB=-0.976-=/SUB=-O-=SUB=-3-=/SUB=-

2021 ◽  
Vol 63 (10) ◽  
pp. 1553
Author(s):  
С.Б. Вахрушев ◽  
Ю.А. Бронвальд ◽  
К.А. Петрухно ◽  
С.А. Удовенко ◽  
И.Н. Леонтьев ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Theoretical Analysis ◽  
Curie Temperature ◽  
Inelastic Scattering ◽  
Brillouin Zone ◽  
Soft Mode ◽  
Mode Frequency ◽  
Structural Factors ◽  
Critical Excitation ◽  
Group Theoretical Analysis

The antiferrodistortive soft mode was detected at the M point of the Brillouin zone in a crystal PbZr0.024Ti0.976O3 using the method of inelastic scattering of synchrotron radiation. The performed group-theoretical analysis and calculations of inelastic structural factors made it possible to relate the detected critical excitation to oxygen octahedra rotations. The traced temperature evolution of the soft mode frequency obeys the Curie-Weiss law with Curie temperature T AFD = 438 ± 5 K, which is close to the ferroelectric Curie temperature T FE = 479.5 K.

Crystal field splitting in the far infrared spectrum of rhombic sulfur

1969 ◽  
Vol 47 (14) ◽  
pp. 2713-2715 ◽  
Author(s):  
A. Anderson ◽  
L. Y. Wong
Keyword(s):  
Theoretical Analysis ◽  
Infrared Spectrum ◽  
Crystal Field ◽  
Far Infrared ◽  
Unit Cell ◽  
Crystal Field Splitting ◽  
Lattice Vibrations ◽  
Normal Coordinate ◽  
Thin Polycrystalline ◽  
Group Theoretical Analysis

The infrared (i.r.) spectra of thin polycrystalline samples of orthorhombic sulfur at 95 °K in the range 50–500 cm−1 have been recorded. The three i.r. active fundamentals ν4, ν5, and ν6 are observed to be split into 2,3, and 3 components, respectively, as predicted from a group theoretical analysis of the unit cell symmetry, thus confirming the assignment of ν4 and ν6. Several weaker absorptions are assigned by comparison with recent Raman results and a normal coordinate analysis. No peaks assignable to lattice vibrations are observed.

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