Group theoretical analysis of lattice vibrations in molecular crystals

Pramana ◽  
1977 ◽  
Vol 9 (2) ◽  
pp. 189-202
Author(s):  
N Krishnamurthy
Keyword(s):  
Theoretical Analysis ◽  
Molecular Crystals ◽  
Lattice Vibrations ◽  
Group Theoretical Analysis

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

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.

scholarly journals Phonons in Short-Period GaN/AlN Superlattices: Group-Theoretical Analysis, Ab initio Calculations, and Raman Spectra

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 286
Author(s):  
Valery Davydov ◽  
Evgenii Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Raman Spectra ◽  
Density Functional ◽  
Structural Characteristics ◽  
Vibrational Modes ◽  
Phonon Modes ◽  
Short Period ◽  
Group Theoretical Analysis

We report the results of experimental and theoretical studies of phonon modes in GaN/AlN superlattices (SLs) with a period of several atomic layers, grown by submonolayer digital plasma-assisted molecular-beam epitaxy, which have a great potential for use in quantum and stress engineering. Using detailed group-theoretical analysis, the genesis of the SL vibrational modes from the modes of bulk AlN and GaN crystals is established. Ab initio calculations in the framework of the density functional theory, aimed at studying the phonon states, are performed for SLs with both equal and unequal layer thicknesses. The frequencies of the vibrational modes are calculated, and atomic displacement patterns are obtained. Raman spectra are calculated and compared with the experimental ones. The results of the ab initio calculations are in good agreement with the experimental Raman spectra and the results of the group-theoretical analysis. As a result of comprehensive studies, the correlations between the parameters of acoustic and optical phonons and the structure of SLs are obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy. The results obtained can be used to optimize the growth technologies aimed to form structurally perfect short-period GaN/AlN SLs.

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