اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLow-frequency Raman scattering in model disordered solids: percolators above threshold
65
0
0.0
(
0
)
تأليف
O. Pilla
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The Raman coupling coefficients of site- and bond-percolators at concentration higher than percolation threshold are computed for two scattering mechanisms: Bond Polarizability (BPOL) and Dipole-Induced-Dipole (DID). The results show that DID does not follow a scaling law at low frequency, while in the case of BPOL the situation is less clear. The numerically computed frequency dependence in the case of BPOL, which can be considered a good scattering mechanism for a wide class of real glasses, is in semiquantitative agreement with experimental results.
قيم البحث
اقرأ أيضاً
We report new inelastic Raman and neutron scattering spectra for glasses with different degrees of fragility; the data are compared for each sample to obtain the Raman coupling function $C(omega)$. The study indicates a general linear behaviour of th
e $C(omega)$ near the Boson peak maximum, and evidence a correlation between vibrational and relaxational properties, already observed in recent publications.
We show that the low-frequency regime of the density of states of structural glass formers is crucially sensitive to the stress-ensemble from which the configurations are sampled. Specifically, in two dimensions, an exactly isotropic ensemble with ze
ro shear stress fluctuations, displays a $D(omega_{min}) sim omega^{5}_{min}$ regime, as opposed to the $omega^{4}_{min}$ regime observed under unstrained conditions. We also study an ensemble of strained amorphous solids near a plastic event. We show that the minimum eigenvalue distribution at a strain $gamma$ near the plastic event occurring at $gamma_{P}$, displays a collapse when scaled by $sqrt{gamma_P - gamma}$, and with the number of particles as $N^{-0.22}$. Notably, at low-frequencies, this scaled distribution displays a robust $D(omega_{min}) sim omega^{6}_{min}$ power-law regime, which survives in the large $N$ limit. Finally, we probe the universal properties of this ensemble through a characterization of the second and third eigenvalues of the Hessian matrix near a plastic event.
We study a recently introduced and exactly solvable mean-field model for the density of vibrational states $mathcal{D}(omega)$ of a structurally disordered system. The model is formulated as a collection of disordered anharmonic oscillators, with ran
dom stiffness $kappa$ drawn from a distribution $p(kappa)$, subjected to a constant field $h$ and interacting bilinearly with a coupling of strength $J$. We investigate the vibrational properties of its ground state at zero temperature. When $p(kappa)$ is gapped, the emergent $mathcal{D}(omega)$ is also gapped, for small $J$. Upon increasing $J$, the gap vanishes on a critical line in the $(h,J)$ phase diagram, whereupon replica symmetry is broken. At small $h$, the form of this pseudogap is quadratic, $mathcal{D}(omega)simomega^2$, and its modes are delocalized, as expected from previously investigated mean-field spin glass models. However, we determine that for large enough $h$, a quartic pseudogap $mathcal{D}(omega)simomega^4$, populated by localized modes, emerges, the two regimes being separated by a special point on the critical line. We thus uncover that mean-field disordered systems can generically display both a quadratic-delocalized and a quartic-localized spectrum at the glass transition.
Stimulated low-frequency Raman scattering can give essential information about the elastic properties of different nanoparticles systems, in particular, biological nanostructures. In the present study, low-frequency vibrational modes in human and bov
ine serum albumin were for the first time investigated using stimulated low-frequency Raman scattering. Stimulated low-frequency Raman scattering frequency shifts, corresponding to acoustic eigenfrequencies of the sample, were registered by Fabri-Perot interferometers. Conversion efficiency, threshold and set of eigenfrequencies were also measured. Stimulated low-frequency Raman scattering can be applied for biological objects identification and impact on them.
The Raman response of the metallic glass Ni$_{67}$Zr$_{33}$ is measured as a function of polarization and temperature and analyzed theoretically. Unexpectedly, the intensity in the range up to 300wn increases upon cooling, which is counterintuitive w
hen the response originates from vibrations alone as in insulators. The increase finds a natural explanation if the conduction electrons are assumed to scatter on localized vibrations with a scattering probability proportional to the Debye-Waller factor. None of our assumptions is material specific, and the results are expected to be relevant for disordered systems in general.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
