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arXiv 2202.00218cond-mat.softcond-mat.mtrl-scicond-mat.othercond-mat.stat-mechphysics.app-ph
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金属玻璃薄膜中空间非均匀动力学的约束效应

Confinement effects on the spatially inhomogeneous dynamics in metallic glass films

Anh D. Phan

摘要:

我们发展了Elementary集体非线性Langevin方程理论,首次研究了加盖金属玻璃薄膜的玻璃动力学。计算了在不同温度和玻璃化标准下,晶体尺寸对结构弛豫时间和玻璃化转变温度(Tg)空间梯度的影响。分子动力学在粗糙固体表面附近显著减慢,而远离界面的位置处的动力学加快。在厚膜中,由于两个表面之间的干涉效应很弱,因此由体值归一化的迁移率梯度很好地服从双指数形式。薄膜厚度的减小导致了两个表面之间的强动力学耦合,并减小了弛豫梯度。玻璃化转变温度的归一化梯度与玻璃化时间尺度无关,并且可以用叠加函数拟合,因为薄膜不是超薄的。局部脆弱性被发现保持不变的位置。这一发现表明,可以使用Angell图的体弛豫时间和玻璃化温度的空间梯度来表征金属玻璃膜中的玻璃态动力学。我们的计算结果与实验数据和模拟吻合得很好。

英文摘要:

We develop the Elastically Collective Nonlinear Langevin Equation theory to investigate, for the first time, glassy dynamics in capped metallic glass thin films. Finite-size effects on the spatial gradient of structural relaxation time and glass transition temperature (Tg) are calculated at different temperatures and vitrification criteria. Molecular dynamics is significantly slowed down near rough solid surfaces and the dynamics at location far from the interfaces is sped up. In thick films, the mobility gradient normalized by the bulk value well obeys the double-exponential form since interference effects between two surfaces are weak. Reducing the film thickness induces a strong dynamic coupling between two surfaces and flattens the relaxation gradient. The normalized gradient of the glass transition temperature is independent of vitrification timescale criterion and can be fitted by a superposition function as the films are not ultra-thin. The local fragility is found to remain unchanged with location. This finding suggests that one can use Angell plots of bulk relaxation time and the Tg spatial gradient to characterize glassy dynamics in metallic glass films. Our computational results agree well with experimental data and simulation.

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