Abstract

Many of the special properties of nanoparticles (NPs) and nanomaterials broadly derive from the significant fraction of particles (atoms, molecules or segments of polymeric molecules) in the NP interfacial region in which the interparticle interactions are characteristically highly anharmonic in comparison to the bulk material. This leads to relatively large mean square particle displacements relative to the material interior, often resulting in a strong increase interfacial mobility and reactivity in both crystalline and glass NPs. The ‘Debye–Waller factor’, or the mean square particle displacement \(<u^{2}>\) on a ps ‘caging’ timescale relative to the square of the average interparticle distance \(\upsigma ^{2}\), provides an often experimentally accessible measure of the strength of this anharmonic interaction. The Localization Model (LM) of the dynamics of condensed materials relates this thermodynamic property to the structural relaxation time \(\tau _{\alpha }\), determined from the intermediate scattering function, without any free parameters. Moreover, the LM allows for the prediction of the diffusion coefficient D when combined with the ‘decoupling’ or Fractional Stokes-Einstein relation linking \(\tau _{\alpha }\) to D. In the current study, we employed classical molecular dynamics simulation to investigate the structural relaxation and diffusion of model \(\hbox {Cu}_{\mathrm {64}}\hbox {Zr}_{\mathrm {36}}\) metallic glass and Cu crystalline NPs with different sizes. As with previous studies validating the LM on model bulk and crystalline materials, and for the interfacial dynamics of thin crystalline and metallic glass films, we find the LM model also describes the interfacial dynamics of model crystalline metal (Cu) and metallic glass (\(\hbox {Cu}_{\mathrm {64}}\hbox {Zr}_{\mathrm {36}})\) NPs to a good approximation, further confirming the generality of the model.

Graphic abstract

中文翻译：

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晶体Cu和$$ \ hbox {Cu} _ {64} \ hbox {Zr} _ {36} $$ Cu 64 Zr 36金属玻璃纳米粒子界面动力学的本地化模型描述

摘要

纳米颗粒（NPs）和纳米材料的许多特殊性质广泛地源自NP界面区域中的大部分颗粒（原子，分子或聚合物分子链段），与大块材料相比，在该颗粒区域中，颗粒间的相互作用具有高度非谐性。这导致相对于材料内部的相对较大的均方粒子位移，通常会导致晶体和玻璃NP中界面迁移率和反应性的显着提高。在“德拜-沃勒因子”，或均方粒子位移\（<U ^ {2}> \）上的PS“进行封闭而”相对于平均粒子间距离的平方的时间尺度\（\ upsigma ^ {2} \ ），提供了这种非谐交互作用强度的常用实验方法。冷凝材料动力学的局部化模型（LM）将此热力学特性与结构弛豫时间\（\ tau _ {\ alpha} \）关联，该弛豫时间由中间散射函数确定，没有任何自由参数。此外，LM允许扩散系数的预测d当与“脱钩”或分数斯托克斯-爱因斯坦关系联组合\（\ tau蛋白_ {\阿尔法} \）到d。在当前的研究中，我们采用经典的分子动力学模拟来研究模型的结构弛豫和扩散\（\ hbox {Cu} _ {\ mathrm {64}} \ hbox {Zr} _ {\ mathrm {36}} \）金属玻璃和大小不同的Cu晶体NP。与以前的研究验证模型大块和晶体材料上的LM以及薄晶体和金属玻璃薄膜的界面动力学一样，我们发现LM模型还描述了模型晶体金属（Cu）和金属玻璃（\（ \ hbox {Cu} _ {\ mathrm {64}} \ hbox {Zr} _ {\ mathrm {36}}）\） NP近似良好，进一步证实了模型的通用性。

图形摘要