The Anomalies and Local Structure of Liquid Water from Many-Body Molecular Dynamics Simulations

Abstract

For the last 50 years, researchers have sought molecular models that can accurately reproduce water’s microscopic structure and thermophysical properties across broad ranges of its complex phase diagram. Herein, molecular dynamics simulations with the many-body MB-pol model are performed to monitor the thermodynamic response functions and local structure of liquid water from the boiling point down to deeply supercooled temperatures at ambient pressure. The isothermal compressibility and isobaric heat capacity show maxima at ~223 K, in excellent agreement with recent experiments, and the liquid density exhibits a minimum at ~208 K. Furthermore, a local tetrahedral arrangement, where each water molecule accepts and donates two hydrogen bonds, is the most probable hydrogen-bonding topology at all temperatures. This work suggests that MB-pol may provide predictive capability for studies of liquid water’s physical properties across broad ranges of thermodynamic states.

Temperature-Dependent Liquid Water Structure for Individual Micron-Sized, Supercooled Aqueous Droplets with Inclusions

“…42 While low-and high-density liquid terminology has been used to describe supercooled water at high pressures and below the homogeneous freezing point, 40,42 others have described these two states differently including as a "locally favored tetrahedral structure" and a "disordered normal liquid structure" with different number of average hydrogen bonds, 4 and 3, respectively. 43 Raman spectroscopy can be used to probe the hydrogenbonding network of water molecules within aqueous bulk solutions and within individual aqueous droplets. 37,44 The main spectral region of interest is the region between 2800 and 3800 cm −1 (as seen in Figure 1 for micron-sized water droplets on a hydrophobic substrate) that is associated with the O−H stretching motion of water.…”

Maximum in density of electrolyte solutions: Learning about ion–water interactions and testing the Madrid-2019 force field

“…This is illustrated in Fig. 1 and Table I, where the TMD of several realistic water models 45 is presented. [32][33][34][35][36][37][38][39][40][41][42][43][44][45] In addition, Kiss and Baranyai published a relevant work about the TMD of water models.…”

“…1 and Table I, where the TMD of several realistic water models 45 is presented. [32][33][34][35][36][37][38][39][40][41][42][43][44][45] In addition, Kiss and Baranyai published a relevant work about the TMD of water models. 54 The trend is clear: models proposed in the 1970s, 1980s, and 1990s did not reproduce the experimental value of the TMD of water.…”