Raman phonon spectra and lattice dynamics of 7-methoxycoumarin under pressure

1995 ◽  
Vol 246 (6) ◽  
pp. 619-625
Author(s):  
A. Brillante ◽  
R.G. Della Valle ◽  
E. Venuti
Keyword(s):  
Lattice Dynamics ◽  
Phonon Spectra

LATTICE DYNAMICS OF THE BINARY APERIODIC CHAINS OF ATOMS I: FRACTAL DIMENSION OF PHONON SPECTRA

1995 ◽  
Vol 09 (12) ◽  
pp. 1429-1451 ◽  
Author(s):  
WŁODZIMIERZ SALEJDA
Keyword(s):  
Fractal Dimension ◽  
Lattice Dynamics ◽  
Nearest Neighbor ◽  
Average Distance ◽  
Local Maximum ◽  
Fractal Dimensions ◽  
Dimension Formula ◽  
Phonon Spectra ◽  
Wide Range ◽  
Silver Mean

The microscopic harmonic model of lattice dynamics of the binary chains of atoms is formulated and studied numerically. The dependence of spring constants of the nearest-neighbor (NN) interactions on the average distance between atoms are taken into account. The covering fractal dimensions [Formula: see text] of the Cantor-set-like phonon spec-tra (PS) of generalized Fibonacci and non-Fibonaccian aperiodic chains containing of 16384≤N≤33461 atoms are determined numerically. The dependence of [Formula: see text] on the strength Q of NN interactions and on R=mH/mL, where mH and mL denotes the mass of heavy and light atoms, respectively, are calculated for a wide range of Q and R. In particular we found: (1) The fractal dimension [Formula: see text] of the PS for the so-called goldenmean, silver-mean, bronze-mean, dodecagonal and Severin chain shows a local maximum at increasing magnitude of Q and R>1; (2) At sufficiently large Q we observe power-like diminishing of [Formula: see text] i.e. [Formula: see text], where α=−0.14±0.02 and α=−0.10±0.02 for the above specified chains and so-called octagonal, copper-mean, nickel-mean, Thue-Morse, Rudin-Shapiro chain, respectively.

LATTICE DYNAMICS OF THE BINARY APERIODIC CHAINS OF ATOMS III: PROPERTIES OF VIBRATIONAL EIGENVECTORS

1995 ◽  
Vol 09 (12) ◽  
pp. 1475-1501 ◽  
Author(s):  
WŁODZIMIERZ SALEJDA
Keyword(s):  
Elastic Energy ◽  
Lattice Dynamics ◽  
Quantitative Agreement ◽  
Model Parameters ◽  
Harmonic Model ◽  
Energy Field ◽  
Qualitative And Quantitative ◽  
Phonon Spectra ◽  
Multifractal Spectra ◽  
Optical Region

We numerically study the localization and multifractal properties of normalized vibrational eigenvectors (NVEV), denoted by U, of the microscopic harmonic model of lattice dynamics in Thue-Morse (TM), generalized Fibonacci, octagonal, dodecagonal, Severin, circle and Rudin-Shapiro (RS) binary chain of atoms. Eigenvalues and NVEV are determined with the help of the Dean and Wu-Zheng algorithm, respectively, with free end boundary conditions for chains containing 103<N<104 atoms. The first FM(L) and second SM(L) moment, and the reduced participation ratios Λ red (L) are derived at 1≤L≤N for varying model parameters. All the chains studied show sinusoidal-like and packet-like extended NVEV with Λred(L)≃1, FM(L)≃N/2 and [Formula: see text] The new extended eigenstates called dimmerized NVEV have been found out in the case of the TM chain. The surface localized NVEV with Λred(L)≪1, FM(L)≃1 or FM(L)≃N and the strong tendency to localization of NVEV in RS chain have been observed. The critical NVEV, which dominate in the optical region of phonon spectra, are objects with a broad multifractal (αmin, αmax) spectra. If magnitudes of model parameters are increased then, first, [Formula: see text] and [Formula: see text] at L≪N and, second, [Formula: see text] and [Formula: see text] at L≃N. It is numerically shown that the multifractal spectra α′—f′ characterizing the curdling of the elastic energy field ε(L) are in excellent qualitative and quantitative agreement with the multifractal spectra of the critical NVEV.

Phonon spectra of ortho -dinitrotetramethylbenzene crystals

1987 ◽  
Vol 65 (9) ◽  
pp. 2122-2125 ◽  
Author(s):  
Paolo Sgarabotto ◽  
Mario Braghetti ◽  
Rosario Sergio Cataliotti ◽  
Giulio Paliani ◽  
Salvatore Sorriso ◽  
...  
Keyword(s):  
Group Theory ◽  
Phase Transitions ◽  
Solid State ◽  
Melting Point ◽  
Nitro Group ◽  
Vibrational Spectra ◽  
Lattice Dynamics ◽  
Solid Phase ◽  
Methyl Group ◽  
Phonon Spectra

We have studied the vibrational spectra and thermal behaviour of ortho-dinitrotetramethylbenzene (o-DNTMB) to learn more about its molecular and lattice dynamics. The molecule undergoes two solid–solid phase transitions, close to the melting point, which could be explained by the relaxation of forces hindering the methyl-group and nitro-group free rotations. We have deduced the nature of the solid state vibrational motions, particularly those of lattice phonons, using group theory.

Lattice dynamics of rare-gas solids by Kihara's potential: I. Phonon spectra

1975 ◽  
Vol 68 (1) ◽  
pp. 307-317 ◽  
Author(s):  
T. N. Agrawal ◽  
R. K. Gupta ◽  
G. L. Gupta
Keyword(s):  
Lattice Dynamics ◽  
Rare Gas ◽  
Phonon Spectra

Lattice dynamics of heavy rare-gas solids

1969 ◽  
Vol 47 (6) ◽  
pp. 617-625 ◽  
Author(s):  
N. P. Gupta ◽  
R. K. Gupta
Keyword(s):  
Iterative Method ◽  
Specific Heat ◽  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Zero Point ◽  
Central Force ◽  
Experimental Results ◽  
Rare Gas ◽  
Buckingham Potential ◽  
Phonon Spectra

Phonon spectra, dispersion curves, and the specific heat of frozen argon, krypton, and xenon have been studied using a quasiharmonic central force rigid-atom model with interactions up to eighth neighbors. The effect of zero-point vibration is included by an iterative method and a modified Buckingham potential is used. There is reasonable agreement between theoretical and experimental results. A number of possibilities for the improvement of results have been discussed.

LATTICE DYNAMICS OF THE BINARY APERIODIC CHAINS OF ATOMS II: MULTIFRACTALITY OF PHONON SPECTRA

1995 ◽  
Vol 09 (12) ◽  
pp. 1453-1474 ◽  
Author(s):  
WŁODZIMIERZ SALEJDA
Keyword(s):  
Lattice Dynamics ◽  
Energy Spectra ◽  
Legendre Transformation ◽  
Model Parameters ◽  
Local Scaling ◽  
Multifractal Formalism ◽  
Phonon Spectra ◽  
Wide Range ◽  
Multifractal Spectra ◽  
Density Of Phonon States

The curdling of the phonon eigenvalues (PEV) on energy spectra of the binary generalized Fibonacci and non-Fibonaccian chains of atoms are numerically studied. A multifractal formalism based upon a new numerically efficient Legendre transformation from (q, τ) to (α, f) variables is proposed. The multifractal spectra of the normalized integrated density of phonon states (NIDOPS) for aperiodic chains of atoms are calculated in a wide range of model parameters. It is found out that the interval (α min , α max ) of magnitudes of the exponent α, determining the local scaling of the NIDOPS, shows a considerable shift to smaller values. This tendency is most pronounced for the NIDOPS of the so-called copper-mean, nickel-mean, structural circle and Rudin-Shapiro chain, where 0<α min <0.1. It is verified numerically that this effect is a manifestation of a strong curdling of PEV which take place in optical regions of the phonon spectra.

Sign in / Sign up

Export Citation Format

Share Document