• Acta Physica Sinica
  • Vol. 69, Issue 6, 066101-1 (2020)
Zhen-Wei Wu1、* and Wei-Hua Wang2
Author Affiliations
  • 1School of Systems Science, Beijing Normal University, Beijing 100875, China
  • 2Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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    DOI: 10.7498/aps.69.20191870 Cite this Article
    Zhen-Wei Wu, Wei-Hua Wang. Linking local connectivity to atomic-scale relaxation dynamics in metallic glass-forming systems[J]. Acta Physica Sinica, 2020, 69(6): 066101-1 Copy Citation Text show less

    Abstract

    For a long time, it has been well recognized that there exists a deep link between the fast vibrational excitations and the slow diffusive dynamics in glass-forming systems. However, it remains as an open question whether and how the short-time scale dynamics associated with vibrational intrabasin excitations is related to the long-time dynamics associated with diffusive interbasin hoppings. In this paper we briefly review the research progress that addresses this challenge. By identifying a structural order parameter—local connectivity of a particle which is defined as the number of nearest neighbors having the same local spatial symmetry, it is found that the local connectivity can tune and modulate both the short-time vibrational dynamics and the long-time relaxation dynamics of the studied particles in a model of metallic supercooled liquid. Furthermore, it reveals that the local connectivity leads the long-time decay of the correlation functions to change from stretched exponentials to compressed ones, indicating a dynamic crossover from diffusive to hyperdiffusive motions. This is the first time to report that in supercooled liquids the particles with particular spatial symmetry can present a faster-than-exponential relaxation that has so far only been reported in out-of-equilibrium materials. The recent results suggest a structural bridge to link the fast vibrational dynamics to the slow structural relaxation in glass-forming systems and extends the compressed exponential relaxation phenomenon from earlier reported out-of-equilibrium materials to the metastable supercooled liquids.
    $ S({{q}})\equiv\frac{1}{N}\left < \hat{\rho}_{{q}}\hat{\rho}_{ -{{q}}}\right >, $(1)

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    $ \begin{split} & S({{q}}) = \frac{1}{N}\left < \sum\limits_{i = 1}^N{\rm e}^{{\rm{i}}{{{q}}\cdot {{r}}_i}}\sum\limits_{j = 1}^N{\rm e}^{-{\rm{i}}{{{q}}\cdot {{r}}_j}}\right > \\ = & \frac{1}{N}\left < \left|\sum\limits_{i = 1}^N\cos({{{q}}\cdot {{r}}_i})\right|^2+ \left|\sum\limits_{i = 1}^N\sin({{{q}}\cdot {{r}}_i})\right|^2\right >, \end{split} $(2)

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    $ S(q) = 1+4{\text{π}}\int_0^{\infty}{\rm{d}}r(g(r)-1)r^2\frac{\sin(qr)}{qr}. $(3)

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    $ { {MSD}} = \frac{1}{N}\left < \sum\limits_{i = 1}^N\left|{{r}}_i(t)-{{r}}_i(0)\right|^2\right >, $(4)

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    $\begin{split} F(q,t) \; & = \frac{1}{N}\left < \rho_{ -{{q}}}(0)\rho_{{{q}}}(t)\right > \\ &= \frac{1}{N}\left < \sum\nolimits_{ij}{\rm e}^{-{\rm{i}}{{{q}}\cdot {{r}}}_i(0)}{\rm e}^{{\rm{i}}{{{q}}\cdot {{r}}}_j(t)}\right >,\end{split}$(5)

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    $ H_{i\alpha j\beta} = \left.\frac{\partial^2V({{r}}^N)} {\partial r_i^{\alpha}\partial r_j^{\beta}}\right|_{\rm{IS}}, $(6)

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    $ D(\omega) = \int {\rm{d}}t\frac{\left < {{v}}_i(0)\cdot{{v}}_i(t)\right > } {\left < {{v}}_i(0)\cdot{{v}}_i(0)\right > }\exp({\rm{i}}\omega t), $(7)

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    $ F_{\rm{s}}(q, t) = \dfrac{1}{N_k} \bigg\langle\sum_j \exp\{{\rm{i}}{{q}}\cdot[{{r}}_j(t)-{{r}}_j(0)]\}\bigg\rangle, $()

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    $ D_k(\omega) = \frac{1}{3n_k}\sum\limits_{i = 1}^{n_k}\sum\limits_{l = 1}^{3N}|{ e}_l^{i}|^2 \text{δ} (\omega-\omega_l), $(8)

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    $ F_{\rm{s}}(q,t)\propto \sum\limits_{i = {\rm{L}},{\rm{H}}} C_i\exp\{{\rm{i}}q[A \cos(\omega_i t+\delta_i)-A \cos(\delta_i)]\}, $(9)

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    $ F_{\rm s}(q,t)\propto A_q\exp[-(t/\tau)^{\beta}], $(10)

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    Zhen-Wei Wu, Wei-Hua Wang. Linking local connectivity to atomic-scale relaxation dynamics in metallic glass-forming systems[J]. Acta Physica Sinica, 2020, 69(6): 066101-1
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