Universality of hydrogen bond distributions in liquid and supercritical water

Abstract

International audienceMonte Carlo and molecular dynamics computer simulations using the rigid TIP4P and the flexible BJH intermolecular H2O potentials were carried out for 50 states of supercritical water characterizing a very wide range of thermodynamic conditions, 573 < T < 1273 K; 0.02 < rho < 1.67 g/cm3; 10 < P < 10,000 MPa. Good agreement with available experimental data of the simulated thermodynamic and structural properties give confidence to the quantitative statistical analysis of intermolecular hydrogen bonding under the conditions studied. Energetic, geometric, and angular characteristics of supercritical H-bonds and their distributions at a given temperature remain almost invariant over the entire density range studied from dilute gas-like (~ 0.03 g/cm3) to highly compressed liquid-like (~ 1.5 g/cm3) states. The increase of temperature from ambient to supercritical affects the characteristics of H-bonding in water much more dramatically than the changes in density along any supercritical isotherm. Compared to H-bonds in liquid water under ambient conditions, the H-bonds at 773 K are, on average, 10% weaker, 5% longer, and less linear. Both above and below the H-bonding percolation threshold the fractions of H2O molecules involved in a certain number of H-bonds in liquid and supercritical water closely follow the universal binomial distribution as a function of the average number of H-bonds per one water molecule in the system, as predicted by the independent bond theory. This universal distribution remains intact even when dynamic criteria of H-bonding lifetimes are additionally applied

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

“…Our ab initio calculations at very low-density range (0.02-0.09 g/cm 3 at 350 ∘ C) indicated 0.09-0.25 H-bonds per water molecule. These values are consistent with the trends reported by Kalinichev [43].…”

“…Following the approach of Kalinichev [43], the total Hbonds in the simulation box were expressed as "H-bond total per water molecule" by dividing total H-bonds with 55, the total number of water molecules in the simulation box (Table 2). Kalinichev [43] (using Monte Carlo and classical MD data presented in [38]) calculated the number of Hbonds per molecule in bulk water for a wide range in density over a temperature range of 25-1000 ∘ C. Their calculations showed a near-linear increase in the number of H-bonds as a function of density for bulk water, and a small decrease in their number with increasing temperature for a given density.…”

“…Kalinichev [43] (using Monte Carlo and classical MD data presented in [38]) calculated the number of Hbonds per molecule in bulk water for a wide range in density over a temperature range of 25-1000 ∘ C. Their calculations showed a near-linear increase in the number of H-bonds as a function of density for bulk water, and a small decrease in their number with increasing temperature for a given density. The degree of H-bonding in the bulk fluid is an important parameter to consider when using a geometrical approach to define the hydration of a cluster; in high-density solutions, all water molecules interact via H-bonding, so that hydration defined in this manner becomes infinite.…”

“…The degree of H-bonding in the bulk fluid is an important parameter to consider when using a geometrical approach to define the hydration of a cluster; in high-density solutions, all water molecules interact via H-bonding, so that hydration defined in this manner becomes infinite. This happens when the number of H-bond per water molecule ∼1 at a density of ∼0.4 g/cm 3 over the 300-600 ∘ C temperature range [43], that is, slightly above the critical density of water (0.32 g/cm 3 ). At fluids density of ∼1 g/cm 3 , the theoretical percolation threshold for the network of hydrogen bonds in water is known to be ∼1.4-1.7, which has since been confirmed by multiple molecular simulations [44][45][46] and experiments [47,48].…”

Structure of Hydrated Kaolinite Edge Surfaces: DFT Results and Further Development of the ClayFF Classical Force Field with Metal–O–H Angle Bending Terms

“…Therefore, for all HB pairs, we consider a uniform H···O acceptor cutoff distance of R HB = 2.45 Å, which is also the generally accepted value for water–water H-bonds . Additionally, for all the reported HBs, the average O donor –H···O acceptor angle was greater than 130°, which is also consistent with the angular range of HBs in bulk liquid water (see, e.g., ref ).…”