Abstract
Many glasses exhibit fractional power law (FPL) between the mean atomic volume va and the first diffraction peak position q1, i.e. v_{mathrm{a}} propto q_1^{ - d} with d ≃ 2.5 deviating from the space dimension D = 3, under compression or composition change. What structural change causes such FPL and whether the FPL and d are universal remain controversial. Here our simulations show that the FPL holds in both two- and three-dimensional glasses under compression when the particle interaction has two length scales which can induce nonuniform local deformations. The exponent d is not universal, but varies linearly with the deformable part of soft particles. In particular, we reveal an unexpected crossover regime with d > D from crystal behavior (d = D) to glass behavior (d < D). The results are explained by two types of bond deformation. We further discover FPLs in real space from the radial distribution functions, which correspond to the FPLs in reciprocal space.
Highlights
Many glasses exhibit fractional power law (FPL) between the mean atomic volume va and the first diffraction peak position q1, i.e. va / qÀ1 d with d ≃ 2.5 deviating from the space dimension D = 3, under compression or composition change
We summarize five open questions: (1) Does the FPL generally hold in glasses? (2) Which factors affect the value of d? (3) What is the origin of the FPL? The anomalous FPLs have been attributed to atomic-scale fractal packing[8] and mediumrange order[6], but both explanations are derived from a single state, not from a series of states as the FPL arises
16 Here we explore the crossover of the power law from crystal behavior (d = D) to glass behavior (d < D) for the first time
Summary
Many glasses exhibit fractional power law (FPL) between the mean atomic volume va and the first diffraction peak position q1, i.e. va / qÀ1 d with d ≃ 2.5 deviating from the space dimension D = 3, under compression or composition change. A well-known puzzle is the fractional power law (FPL) in the reciprocal space of many metallic glasses[3,6], whose mechanism and generality remain controversial[3,6,7,8,9]. Besides the FPL in reciprocal space, other structural power laws have been observed in real space, e.g. based on the distances between neighbors in a granular glass[13] and the correlations of structural order parameters in supercooled liquids[14]. We discover a new set of FPLs in real space that correlates with the FPLs in reciprocal space
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