Transverse Viscous Transport in Classical Solid States,Physical Review Letters

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Transverse Viscous Transport in Classical Solid States
Physical Review Letters ( IF 8.1 ) Pub Date : 2021-12-06 , DOI: 10.1103/physrevlett.127.245901
Akira Furukawa ₁

Affiliation

The transverse velocity time correlation function

{\tilde{C}}_{T} (k, ω)

with

k

and

ω

being the wave number and the frequency, respectively, is a fundamental quantity in determining the transverse mechanical and transport properties of materials. In ordinary liquids, a nonzero value of

{\tilde{C}}_{T} (k, 0)

is inevitably linked to viscous material flows. Even in solids where significant material flows are precluded due to almost frozen positional degrees of freedom, our molecular dynamics simulations reveal that

{\tilde{C}}_{T} (k, 0)

takes a nonzero value, whereby the time integration of the velocity field shows definite diffusive behavior with diffusivity

{\tilde{C}}_{T} (k, 0) / 3

. This behavior is attributed to viscous transport accompanying a small random convection of the velocity field (the inertia effect), and the resultant viscosity is measurable in the Eulerian description: the constituent particles that substantially carry momenta fluctuate slightly around their reference positions. In the Eulerian description, the velocity field is explicitly associated with such fluctuating instantaneous particle positions, whereas in the Lagrangian description, this is not the case. The present study poses a fundamental problem for continuum mechanics: reconciling liquid and solid descriptions in the limit of the infinite structural relaxation time.

中文翻译：

经典固体中的横向粘性输运

横向速度时间相关函数

{\overset{～}{C}}_{吨} (克, ω)

和

克

和

ω

波数和频率分别是决定材料横向力学和输运特性的基本量。在普通液体中，非零值

{\overset{～}{C}}_{吨} (克, 0)

不可避免地与粘性物质流有关。即使在固体中，由于几乎冻结的位置自由度，大量的材料流动被排除，我们的分子动力学模拟显示

{\overset{～}{C}}_{吨} (克, 0)

取非零值，由此速度场的时间积分显示具有扩散率的确定扩散行为

{\overset{～}{C}}_{吨} (克, 0) / 3

. 这种行为归因于伴随速度场的小随机对流（惯性效应）的粘性输运，并且由此产生的粘性在欧拉描述中是可测量的：基本上携带动量的组成粒子围绕其参考位置略微波动。在欧拉描述中，速度场与这种波动的瞬时粒子位置明确相关，而在拉格朗日描述中，情况并非如此。目前的研究为连续介质力学提出了一个基本问题：在无限结构弛豫时间的限制下协调液体和固体的描述。

更新日期：2021-12-06

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