Abstract
Based on recent experimental data that can be interpreted as indicating the presence of specific structures in liquid water, we build and optimize two structural models which we compare with the available experimental data. To represent the proposed high-density liquid structures, we use a model consisting of chains of water molecules, and for low-density liquid, we investigate fused dodecahedra as templates for tetrahedral fluctuations. The computed infrared spectra of the models are in very good agreement with the extracted experimental spectra for the two components, while the extracted structures from molecular dynamics (MD) simulations give spectra that are intermediate between the experimentally derived spectra. Computed x-ray absorption and emission spectra as well as the O-O radial distribution functions of the proposed structures are not contradicted by experiment. The stability of the proposed dodecahedral template structures is investigated in MD simulations by seeding the starting structure, and remnants found to persist on an ∼30 ps time scale. We discuss the possible significance of such seeds in simulations and whether they can be viable candidates as templates for structural fluctuations below the compressibility minimum of liquid water.
Highlights
Water is fundamental to life and our environment, where most processes take place in the presence of water
The proposal that the origin of the anomalous behavior of liquid water could be due to two different forms of the liquid, a high-density liquid (HDL) and a low-density liquid (LDL), is of particular interest in this context
This connection was confirmed by following the transition using wide-angle x-ray scattering (WAXS) as highdensity amorphous (HDA) was heated into the ultraviscous regime and simultaneously using x-ray photon correlation spectroscopy (XPCS) in small-angle x-ray scattering (SAXS) geometry to measure the diffusion constant
Summary
Water is fundamental to life and our environment, where most processes take place in the presence of water. The proposal that the origin of the anomalous behavior of liquid water could be due to two different forms of the liquid, a high-density liquid (HDL) and a low-density liquid (LDL), is of particular interest in this context. The two different forms would be related to the two amorphous ices, low-density amorphous (LDA) and highdensity amorphous (HDA), between which a first-order-like phase transition in pressure has been observed.. The two different forms would be related to the two amorphous ices, low-density amorphous (LDA) and highdensity amorphous (HDA), between which a first-order-like phase transition in pressure has been observed.17–20 This connection was confirmed by following the transition using wide-angle x-ray scattering (WAXS) as HDA was heated into the ultraviscous regime and simultaneously using x-ray photon correlation spectroscopy (XPCS) in small-angle x-ray scattering (SAXS) geometry to measure the diffusion constant.. The two different forms would be related to the two amorphous ices, low-density amorphous (LDA) and highdensity amorphous (HDA), between which a first-order-like phase transition in pressure has been observed. Recently, this connection was confirmed by following the transition using wide-angle x-ray scattering (WAXS) as HDA was heated into the ultraviscous regime and simultaneously using x-ray photon correlation spectroscopy (XPCS) in small-angle x-ray scattering (SAXS) geometry to measure the diffusion constant. the liquid-liquid transition has been evidenced directly in the ultraviscous regime, and in
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