Universality of the Nonphononic Vibrational Spectrum across Different Classes of Computer Glasses

Riedl, David; González-López, Karina; Kapteijns, Geert; Pater, Robert; Vaknin, Talya; Bouchbinder, Eran; Lerner, Edan

doi:10.1103/physrevlett.125.085502

Cited by 89 publications

(125 citation statements)

References 50 publications

(68 reference statements)

Supporting

Mentioning

117

Contrasting

Order By: Relevance

“…As such, the KHGPS Hamiltonian in Eq. (1) appears to offer a relatively simple model for the emergence of the universal D(ω) ∼ ω 4 nonphononic spectra, previously observed in finite-dimensional, particle-based computer glass-formers [10][11][12][13][14][15]18].…”

Section: Discussionmentioning

confidence: 79%

“…1a) emerge from self-organized glassy frustration [8], which is generic to structural glasses quenched from a melt [9]. Their associated frequencies ω have been shown [10][11][12] to follow a universal nonphononic (non-Debye) density of states D(ω)∼ω 4 as ω→0, independently of microscopic details [13,14], spatial dimension [15,16] and formation history [17,18]. Some examples for D(ω), obtained in computer glasses, are shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mean-field model of interacting quasilocalized excitations in glasses

et al. 2021

Self Cite

View full text Add to dashboard Cite

Structural glasses feature quasilocalized excitations whose frequencies \omegaω follow a universal density of states {D}(\omega)\!\sim\!\omega^4D(ω)∼ω4. Yet, the underlying physics behind this universality is not fully understood. Here we study a mean-field model of quasilocalized excitations in glasses, viewed as groups of particles embedded inside an elastic medium and described collectively as anharmonic oscillators. The oscillators, whose harmonic stiffness is taken from a rather featureless probability distribution (of upper cutoff \kappa_0κ0) in the absence of interactions, interact among themselves through random couplings (characterized by a strength JJ) and with the surrounding elastic medium (an interaction characterized by a constant force hh). We first show that the model gives rise to a gapless density of states {D}(\omega)\!=\!A_{g}\,\omega^4D(ω)=Agω4 for a broad range of model parameters, expressed in terms of the strength of the oscillators’ stabilizing anharmonicity, which plays a decisive role in the model. Then — using scaling theory and numerical simulations — we provide a complete understanding of the non-universal prefactor A_{g}(h,J,\kappa_0)Ag(h,J,κ0), of the oscillators’ interaction-induced mean square displacement and of an emerging characteristic frequency, all in terms of properly identified dimensionless quantities. In particular, we show that A_{g}(h,J,\kappa_0)Ag(h,J,κ0) is a non-monotonic function of JJ for a fixed hh, varying predominantly exponentially with -(\kappa_0 h^{2/3}\!/J^2)−(κ0h2/3/J2) in the weak interactions (small JJ) regime — reminiscent of recent observations in computer glasses — and predominantly decays as a power-law for larger JJ, in a regime where hh plays no role. We discuss the physical interpretation of the model and its possible relations to available observations in structural glasses, along with delineating some future research directions.

show abstract

Section: Discussionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Mean-field model of interacting quasilocalized excitations in glasses

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, since the saddle modes progressively stabilize at low temperature, it is natural to inquire the connection between them and the stable modes populating the lowfrequency portion of the vibrational spectrum. The lowest-frequency modes of local minima display quasi-localized vibrations (QLVs) [29,30], which are at present much better understood than the unstable saddle modes [29][30][31][32][33][34][35][36][37]. QLVs consist of an energetically unstable core and a stable far-field [38] and their eigenenergy is determined by the competition between these two components.…”

Section: Introductionmentioning

confidence: 99%

Spatial structure of unstable normal modes in a glass-forming liquid

et al. 2021

View full text Add to dashboard Cite

The phenomenology of glass-forming liquids is often described in terms of their underlying, high-dimensional potential energy surface. In particular, the statistics of stationary points sampled as a function of temperature provides useful insight into the thermodynamics and dynamics of the system. To make contact with the real space physics, however, analysis of the spatial structure of the normal modes is required. In this work, we numerically study the potential energy surface of a glass-forming ternary mixture. Starting from liquid configurations equilibrated over a broad range of temperatures using a swap Monte Carlo method, we locate the nearby stationary points and investigate the spatial architecture and the energetics of the associated unstable modes. Through this spatially-resolved analysis, originally developed to study local minima, we corroborate recent evidence that the nature of the unstable modes changes from delocalized to localized around the mode-coupling temperature. We find that the displacement amplitudes of the delocalized modes have a slowly decaying far field, whereas the localized modes consist of a core with large displacements and a rapidly decaying far field. The fractal dimension of unstable modes around the mobility edge is equal to 1, consistent with the scaling of the participation ratio. Finally, we find that around and below the mode-coupling temperature the unstable modes are localized around structural defects, characterized by a disordered local structure markedly different from the liquid's locally favored structure. These defects are similar to those associated to quasi-localized vibrations in local minima and are good candidates to predict the emergence of localized excitations at low temperature.

show abstract

“…Structural disorder in glassy materials gives rise to physical phenomena absent from their ordered crystalline counterparts. A notable example is the emergence of quasilocalized modes, either in the form of low-frequency nonphononic excitations in the absence of external driving forces [1][2][3][4][5][6][7][8][9][10][11][12] or in the form of quasilocalized irreversible (plastic) rearrangements under external driving forces [13][14][15][16][17][18]. Quasilocalized modes feature a short-range disordered core and long-range decaying displacement fields.…”

mentioning

confidence: 99%

“…As the core size a is microscopic in nature, typically of the order of a few atomic lengths, the short-range core properties are inaccessible in laboratory molecular glasses. As a result, computer simulations of model glasses play a central role in exploring the physics of quasilocalized modes [3][4][5][6][7][8][9][10][11][12]15,16,[40][41][42]. Yet, to the best of our knowledge, we still lack systematic, robust, and efficient approaches for extracting the short-range core properties in computer glasses.…”

mentioning

confidence: 99%

Extracting the properties of quasilocalized modes in computer glasses: Long-range continuum fields, contour integrals, and boundary effects

et al. 2020

Self Cite

View full text Add to dashboard Cite

Low-frequency nonphononic modes and plastic rearrangements in glasses are spatially quasilocalized, i.e., they feature a disorder-induced short-range core and known long-range decaying elastic fields. Extracting the unknown short-range core properties, potentially accessible in computer glasses, is of prime importance. Here we consider a class of contour integrals, performed over the known long-range fields, which are especially designed for extracting the core properties. We first show that, in computer glasses of typical sizes used in current studies, the long-range fields of quasilocalized modes experience boundary effects related to the simulation box shape and the widely employed periodic boundary conditions. In particular, image interactions mediated by the box shape and the periodic boundary conditions induce the fields' rotation and orientation-dependent suppression of their long-range decay. We then develop a continuum theory that quantitatively predicts these finite-size boundary effects and support it by extensive computer simulations. The theory accounts for the finite-size boundary effects and at the same time allows the extraction of the short-range core properties, such as their typical strain ratios and orientation. The theory is extensively validated in both two and three dimensions. Overall, our results offer a useful tool for extracting the intrinsic core properties of nonphononic modes and plastic rearrangements in computer glasses.

show abstract

Universality of the Nonphononic Vibrational Spectrum across Different Classes of Computer Glasses

Cited by 89 publications

References 50 publications

Mean-field model of interacting quasilocalized excitations in glasses

Mean-field model of interacting quasilocalized excitations in glasses

Spatial structure of unstable normal modes in a glass-forming liquid

Extracting the properties of quasilocalized modes in computer glasses: Long-range continuum fields, contour integrals, and boundary effects

Contact Info

Product

Resources

About