Keanini Russell G, Dahlberg Jerry, Tkacik Peter T
Department of Mechanical Engineering, University of North Carolina at Charlotte, Charlotte, 28078, USA.
Sci Rep. 2021 Jan 28;11(1):2528. doi: 10.1038/s41598-021-82112-8.
Physical arguments and comparisons with published experimental data suggest that in simple liquids: (i) single-molecule-scale viscous forces are produced by temperature-dependent London dispersion forces, (ii) viscosity decay with increasing temperature reflects electron cloud compression and attendant suppression of electron screening, produced by increased nuclear agitation, and (iii) temperature-dependent self-diffusion is driven by a narrow band of phonon frequencies lying at the low-frequency end of the solid-state-like phonon spectrum. The results suggest that collision-induced electron cloud distortion plays a decisive role in single molecule dynamics: (i) electron cloud compression produces short-lived repulsive states and single molecule, self-diffusive hops, while (ii) shear-induced distortion generates viscosity and single-molecule-scale viscous drag. The results provide new insight into nonequilibrium molecular dynamics in nonpolar, nonmetallic liquids.
基于物理原理的论证以及与已发表实验数据的比较表明，在简单液体中：（i）单分子尺度的粘性力由与温度相关的伦敦色散力产生；（ii）粘度随温度升高而衰减反映了电子云压缩以及伴随的电子屏蔽抑制，这是由核运动加剧所导致的；（iii）与温度相关的自扩散由位于类似固态声子谱低频端的窄带声子频率驱动。结果表明，碰撞诱导的电子云畸变在单分子动力学中起决定性作用：（i）电子云压缩产生短寿命的排斥态和单分子自扩散跳跃，而（ii）剪切诱导的畸变产生粘度和单分子尺度的粘性阻力。这些结果为非极性、非金属液体中的非平衡分子动力学提供了新的见解。
