Shull-Wollan Center, University of Tennessee and Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA and Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, 37996, USA.
Department of Integrated Science and Technology, Oita University, Dannoharu, Oita 870-1192, Japan.
Phys Rev E. 2018 Aug;98(2-1):022604. doi: 10.1103/PhysRevE.98.022604.
Even though viscosity is one of the fundamental properties of liquids, its microscopic origin is not fully understood. We determined the spatial and temporal correlation of molecular motions of water near room temperature and its temperature variation on a picosecond timescale and a subnanometer spatial scale, through high-resolution inelastic x-ray scattering measurement. The results, expressed in terms of the time-dependent pair correlation function called the Van Hove function, show that the timescale of the decay of the molecular correlation is directly related to the Maxwell relaxation time near room temperature, which is proportional to viscosity. This conclusion validates our earlier finding that the topological changes in atomic or molecular connectivity are the origin of viscosity in liquids.
尽管粘度是液体的基本性质之一,但它的微观起源还不完全清楚。我们通过高分辨率非弹性 X 射线散射测量,在皮秒时间尺度和亚纳米空间尺度上确定了室温附近水的分子运动的时空相关性及其温度变化。用称为范霍夫函数的时变对关联函数表示的结果表明,分子相关性衰减的时间尺度与室温附近的麦克斯韦弛豫时间直接相关,而麦克斯韦弛豫时间与粘度成正比。这一结论验证了我们之前的发现,即原子或分子连接的拓扑变化是液体粘度的起源。