Log-normal spectrum of low-energy vibrational excitations in glasses

Malinovsky, V. K.; Novikov, V. N.; Sokolov, Alexei P.

doi:10.1016/0375-9601(91)90363-d

Cited by 116 publications

(69 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…To account for the observed asymmetry, we fit it to a log normal function. 77 The remaining peaks in the spectrum were fit to Gaussian functions. Their frequencies and areas are listed in Table III.…”

Section: Experimental Analysis Of Porphine Halide Vibrationsmentioning

confidence: 99%

Spectroscopic identification of reactive porphyrin motions

Barabanschikov

Demidov

Kubo

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

Nuclear resonance vibrational spectroscopy (NRVS) reveals the vibrational dynamics of a Mössbauer probe nucleus. Here, 57 Fe NRVS measurements yield the complete spectrum of Fe vibrations in halide complexes of iron porphyrins. Iron porphine serves as a useful symmetric model for the more complex spectrum of asymmetric heme molecules that contribute to numerous essential biological processes. Quantitative comparison with the vibrational density of states (VDOS) predicted for the Fe atom by density functional theory calculations unambiguously identifies the correct sextet ground state in each case. These experimentally authenticated calculations then provide detailed normal mode descriptions for each observed vibration. All Fe-ligand vibrations are clearly identified despite the high symmetry of the Fe environment. Low frequency molecular distortions and acoustic lattice modes also contribute to the experimental signal. Correlation matrices compare vibrations between different molecules and yield a detailed picture of how heme vibrations evolve in response to (a) halide binding and (b) asymmetric placement of porphyrin side chains. The side chains strongly influence the energetics of heme doming motions that control Fe reactivity, which are easily observed in the experimental signal.

show abstract

Section: Experimental Analysis Of Porphine Halide Vibrationsmentioning

confidence: 99%

Spectroscopic identification of reactive porphyrin motions

Barabanschikov

Demidov

Kubo

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The elastic continuum approximation for the acoustic excitations breaks down on a mesoscopic wavelength comparable to ξ, where a marked reduction of the sound velocity and strong scattering were observed [10,11]. It has been suggested that the elastic heterogeneity is closely linked to several unusual properties of glasses, which include low-temperature thermal properties [12], an excess vibrational density of states, known as the "Boson peak" [13,14], and anomalous acoustic properties [10,11,[15][16][17]. Theoretical models [18,19] have been proposed to relate the boson peak and the associated thermal and acoustic anomalies to a randomly fluctuating shear modulus.…”

Section: Introductionmentioning

confidence: 99%

Measuring spatial distribution of the local elastic modulus in glasses

Mizuno

Mossa²,

Barrat³

2013

Phys. Rev. E

135

166

View full text Add to dashboard Cite

Glasses exhibit spatially inhomogeneous elastic properties, which can be investigated by measuring their elastic moduli at a local scale. Various methods to evaluate the local elastic modulus have been proposed in the literature. A first possibility is to measure the local stress-local strain curve and to obtain the local elastic modulus from the slope of the curve, or equivalently to use a local fluctuation formula. Another possible route is to assume an affine strain and to use the applied global strain instead of the local strain for the calculation of the local modulus. Most recently a third technique has been introduced, which is easy to be implemented and has the advantage of low computational cost. In this contribution, we compare these three approaches by using the same model glass and reveal the differences among them caused by the non-affine deformations.

show abstract

“…The model, studied here, belongs to this class it has further no molecular vibrations or low lying optic modes in its crystalline form. Some authors attribute the BP to vibrations of clusters of atoms of typical sizes [3,4]. The origin of these clusters is unclear and they have not been identified in numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

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

Schober

2004

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

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.

show abstract

Log-normal spectrum of low-energy vibrational excitations in glasses

Cited by 116 publications

References 12 publications

Spectroscopic identification of reactive porphyrin motions

Spectroscopic identification of reactive porphyrin motions

Measuring spatial distribution of the local elastic modulus in glasses

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

Contact Info

Product

Resources

About