Anharmonic potentials and vibrational localization in glasses

Buchenau, U.; Galperin, Y. M.; Гуревич, В. Л.; Schober, H. R.

doi:10.1103/physrevb.43.5039

Cited by 379 publications

(285 citation statements)

References 19 publications

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“…First a QLV (an oscillator in the present description) has typically an atomic participation number of ten or more 18,19 . An oscillator participation number of ten is then equivalent to an atomic participation number of a hundred or more.…”

Section: B Oscillator Participation Numbersmentioning

confidence: 99%

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Pressure dependence of the boson peak in glasses

2005

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The inelastic scattering intensities of glasses and amorphous materials has a maximum at a low frequency, the so called Boson peak. Under applied hydrostatic pressure, P , the Boson peak frequency, ω b , is shifted upwards. We have shown previously that the Boson peak is created as a result of a vibrational instability due to the interaction of harmonic quasi localized vibrations (QLV). Applying pressure one exerts forces on the QLV. These shift the low frequency part of the excess spectrum to higher frequencies. For low pressures we find a shift of the Boson peak linear in P , whereas for high pressures the shift is ∝ P 1/3 . Our analytics is supported by simulation. The results are in agreement with the existing experiments.

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Section: B Oscillator Participation Numbersmentioning

confidence: 99%

“…The latter are the cores of the QLV or "bare QLV" which have been found to extend over several atoms 18,19 . In this basis there is a bilinear interaction which is treated as a perturbation.…”

Section: Introductionmentioning

confidence: 99%

Pressure dependence of the boson peak in glasses

2005

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“…This finding is in agreement with the interpretation of experiments by the soft potential model. 38 From a Monte Carlo study of liquid Se it was concluded that the model provides a sound basis for the study of both the microscopic and the electronic structure, despite some deficiency in the treatment of the van der Waals interaction. 39 During the simulations the pressure was fixed to 0 Pa, i.e., we worked with equilibrium structures.…”

Section: Simulationsmentioning

confidence: 99%

Structure and relaxation in liquid and amorphous selenium

Caprion

Schober

2000

Phys. Rev. B

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We report a molecular dynamics simulation of selenium, described by a three-body interaction. The temperatures T g and T c and the structural properties are in agreement with experiment. The mean nearest neighbor coordination number is 2.1. A small prepeak at about 1 Å Ϫ1 can be explained in terms of void correlations. In the intermediate self-scattering function, i.e., the density fluctuation correlation, classical behavior, ␣ and ␤ regimes, is found. We also observe the plateau in the ␤ regime below T g . In a second step, we investigated the heterogeneous and/or homogeneous behavior of the relaxations. At both short and long times the relaxations are homogeneous ͑or weakly heterogeneous͒. In the intermediate time scale, lowering the temperature increases the heterogeneity. We connect these different domains to the vibrational ͑ballistic͒, ␤ and ␣ regimes. We have also shown that the increase in heterogeneity can be understood in terms of relaxations.

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“…Thus quasi-local vibrations, also called resonant vibrations, are created [16]. Fitting the model to the experimental data, one finds effective masses of 20-100 atomic masses for the entities moving in these effective soft potentials [17].The sound waves in turn will be damped by resonant scattering with these modes [18]. For low frequencies the SPM predicts an increase of the excess of the DOS as Z excess (ω) ∝ ω 4 .…”

Section: Introductionmentioning

confidence: 99%

Vibrations and relaxations in a soft sphere glass: boson peak and structure factors

Schober

2004

J. Phys.: Condens. Matter

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The dynamics of a soft sphere model glass, studied by molecular dynamics, is investigated.The vibrational density of states divided by ω 2 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.

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Anharmonic potentials and vibrational localization in glasses

Cited by 379 publications

References 19 publications

Pressure dependence of the boson peak in glasses

Pressure dependence of the boson peak in glasses

Structure and relaxation in liquid and amorphous selenium

Vibrations and relaxations in a soft sphere glass: boson peak and structure factors

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