A small subset of normal modes mimics the properties of dynamical heterogeneity in a model supercooled liquid

Abstract

In this work, we study the nature of transitions between inherent structures of a two-dimensional model supercooled liquid. We demonstrate that these transitions occur predominately along a small number of directions on the energy landscape. Moreover, we show that the number of such directions decreases as the temperature of the liquid is decreased in the mildly supercooled regime, in concert with earlier studies on an athermal jamming system. We show that this decrease happens in parallel with a change in character of the transitions as dynamics in the system become more heterogeneous and localized. We investigate the origin of these trends, which suggests interesting connections between jamming and thermal glassy phenomena.

Understanding Plastic Deformation in Thermal Glasses from Single-Soft-Spot Dynamics

“…Regions that are particularly effective in scattering sound appear as regions of high polarization in low-frequency quasilocalized vibrational modes. The high-polarization regions have been shown to be vulnerable to rearrangement under applied stress or temperature [2][3][4][5][6][7][8][9]. Manning and Liu [6] therefore used low-frequency quasilocalized modes to construct a population of localized regions, or "soft spots," which they showed were highly correlated with rearrangements induced by quasistatic shear at zero temperature.…”

Identifying Structural Flow Defects in Disordered Solids Using Machine-Learning Methods

“…In disordered solids, it has long been hypothesized that localized particle rearrangements [3] induced by stress or temperature also occur at localized flow defects [4][5][6]. Like dislocations in crystals [7], flow defects in disordered solids are particularly effective in scattering sound waves, so analyses of the low-frequency vibrational modes [8] have been used successfully to demonstrate the existence of localized flow defects [7,[9][10][11][12][13][14][15][16][17]. However, all attempts to identify flow defects [18,19] directly from the structure, without using knowledge of the interparticle interactions, have failed [18,19].…”

The inherent dynamics of a molecular liquid: Geodesic pathways through the potential energy landscape of a liquid of linear molecules

“…There is an alternative that actually does fulfill our goal of having a genuinely microscopic formulation of motion in the full configuration space (and which, in fact, is frequently assumed to be what one means by "inherent dynamics"): 23,24 the sequence of inherent structures quenched from a molecular dynamics trajectory. 12, 23-35 Such a definition is certainly consistent with the inherent-structure notion of looking at behavior stripped of the noise of thermal fluctuations, 2, 23, 25 but while the identification of geodesics with most efficient pathways is derived from a dynamical theory, it is not completely obvious what dynamical significance a sequence of inherent structures has.…”

“…But, at least in the landscape-influenced (as opposed to the landscape-dominated) 37 regimes of ordinary and supercooled liquids, there is no reason to expect most of the tiny local minima of a potential surface to be all that helpful in explaining the time evolution, nor is it clear what kinds of insights into dynamics are obtained by ignoring minima whose spacings are below some arbitrary cut-off. 24,26 While the time-ordered set of local minima obtained by using inherent structures does make for a completely unambiguous and mathematically well-defined coarse graining of the manybody dynamics, the perspective we take is that the geodesic pathways, which are explicitly optimal routes, may reveal more about that dynamics, at least when activated events are not the dominant motif.…”