The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130-350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational rel...

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Bibliographic Details
Published in:The Journal of chemical physics 2015-06, Vol.142 (24), p.244507-244507
Main Authors: Demontis, Pierfranco, Gulín-González, Jorge, Masia, Marco, Sant, Marco, Suffritti, Giuseppe B
Format: Article
Language:English
Subjects:
ATOMS
Chemical bonds
Computer simulation
COMPUTERIZED SIMULATION
CORRELATION FUNCTIONS
Cross correlation
Crossovers
DISTRIBUTION
DISTRIBUTION FUNCTIONS
Dynamic structural analysis
Fluid dynamics
HYDROGEN
Hydrogen bonds
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
Laboratories
LIQUIDS
MATHEMATICAL METHODS AND COMPUTING
Mathematical models
Molecular dynamics
MOLECULAR DYNAMICS METHOD
Molecular Dynamics Simulation
Molecular properties
Molecular structure
MOLECULES
ORDER PARAMETERS
Physical simulation
POTENTIALS
RELAXATION
Rotation
Temperature
TEMPERATURE RANGE 0400-1000 K
WATER
Water - chemistry
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Summary:In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130-350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between "fragile" (at higher temperatures) and "strong" (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between "fragile" (at lower temperatures) and "strong" (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T(∗) ∼ 315 ± 5 K, was spotted at T(∗) ∼ 283 K and T(∗) ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible mechanisms of the two crossovers at molecular level are discussed.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4922930