Lynden-Bell R M, Debenedetti Pablo G
University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, UK.
J Phys Chem B. 2005 Apr 14;109(14):6527-34. doi: 10.1021/jp0458553.
Model liquids have been constructed to study the role of local structure in the anomalous properties of liquid water. The intermolecular potentials were modified by increasing the weight of the Lennard-Jones term relative to the electrostatic term in the SPC/E model for water. The resulting family of liquids varies from SPC/E water to a Lennard-Jones-like liquid. Properties were measured as a function of density and temperature. The local structure was described by two order parameters, one measuring the tetrahedral order and the other measuring the translational order. The translational order parameter was found to be large for both tetrahedral and Lennard-Jones liquids, but to go through a minimum as the potentials were modified, demonstrating that the two types of structure are incompatible. Just as in water several properties (e.g., the translational diffusion coefficient, entropy) exhibit anomalous density dependence as a result of the breakdown of local tetrahedrality, we observed nonmonotonic behavior of the translational diffusion constant and reorientational relaxation rate as the fluids were transformed from tetrahedral to Lennard-Jones-like. This is also an indication of the incompatibility between Lennard-Jones and water-like structure.
已构建模型液体以研究局部结构在液态水异常性质中的作用。通过增加伦纳德 - 琼斯项相对于水的SPC/E模型中静电项的权重来修改分子间势。由此产生的一系列液体从SPC/E水变化到类似伦纳德 - 琼斯的液体。测量了作为密度和温度函数的性质。局部结构由两个序参量描述，一个测量四面体序，另一个测量平移序。发现平移序参量对于四面体液体和伦纳德 - 琼斯液体都很大，但随着势的修改经历一个最小值，表明这两种结构类型不相容。正如在水中由于局部四面体性的破坏，几种性质（例如平移扩散系数、熵）表现出异常的密度依赖性一样，我们观察到随着流体从四面体转变为类似伦纳德 - 琼斯的，平移扩散常数和重取向弛豫速率的非单调行为。这也表明了伦纳德 - 琼斯结构与水状结构之间的不相容性。
