4.1 Problems of Describing the Dynamics of Water on the Basis of Hydrogen Bonds
133
(300 kcal/mol). This energy was not accounted for in the above-calculated strength of
the hydrogen bond. Note that the electrostatic field of ions polarizes the surrounding
species more efficiently than the dipole–dipole interaction and assumes long-range
intermolecular cooperativity, because the electrostatic potential of an ion is proportional to the inverse distance 1/r , but the Van-der-Waals potential is proportional to
1/r
6 . While the latter can be neglected at the intermolecular level, the former provides an additional cohesion of water species on the long-range level, which must
be accounted for.
Eisenberg and Kauzmann [9] analyzed the problems of hydrogen bonding and
concluded that the fraction of broken bonds in the liquid may not be the best parameter
for describing water. For example, the IR spectrum, discussed in Sect. 2.5, is not
compatible with the concept of a discrete number of sharply defined bounded species.
If such species exist, one would expect a contribution from non-hydrogen-bonded
OH groups of H 2 O molecules near the corresponding OH-vibration mode of water
vapor (see Fig. 2.13). However, this was not observed. Moreover, the large dielectric
constant, (0), of water and ice implies strong molecular correlations and a high
polarization ability. These two mechanisms cannot be simultaneously satisfied in
terms of a hydrogen-bonded network of identical long-lived molecular species.
Although some aspects of the complex phenomenon of hydrogen bonding are
still suitable for the description of proton transfer, in general, it is outdated and
does not fully reflect modern spectroscopic data. The dynamics of hydrogen bonds
and Bernal–Fowler water (see Chap. 1) is probably not the best platform for the
analysis of the electrodynamics of water and ice. The concept of molecular water
was developed on the basis of diffusion-averaged dynamics and does not include
short-term (picosecond) high-frequency dynamics, i.e., high-frequency dynamics
assume additional to H 2 O short-lived species [10]. In Sects. 4.2 and 4.3 we discuss
a phenomenological model (the ionic model) of water, in which a variety of specific
bonds of well-defined molecular species are substituted with the simple electrostatic
interaction between the variety of short-lived ions and molecules. Although the ionic
model is yet to be tested and recognized, it looks promising for the explanation of
the anomalous properties of water beyond the electrodynamic data.
4.2 A Phenomenological Model for the Broadband
Dielectric Response
4.2.1 Microscopic Features of Self-diffusion
Frenkel showed [11] that molecules of a liquid undergo Brownian diffusion, being at
the same time in an oscillatory state similar to that in solids. In this way, he reduced
the theoretical gap between solids and liquids, allowing them to be considered on
the same footing. Figure 4.1 shows a snapshot of the relative arrangement of water
molecules estimated by neutron and X-ray diffraction techniques (see Sect. 1.2.3 for
133
(300 kcal/mol). This energy was not accounted for in the above-calculated strength of
the hydrogen bond. Note that the electrostatic field of ions polarizes the surrounding
species more efficiently than the dipole–dipole interaction and assumes long-range
intermolecular cooperativity, because the electrostatic potential of an ion is proportional to the inverse distance 1/r , but the Van-der-Waals potential is proportional to
1/r
6 . While the latter can be neglected at the intermolecular level, the former provides an additional cohesion of water species on the long-range level, which must
be accounted for.
Eisenberg and Kauzmann [9] analyzed the problems of hydrogen bonding and
concluded that the fraction of broken bonds in the liquid may not be the best parameter
for describing water. For example, the IR spectrum, discussed in Sect. 2.5, is not
compatible with the concept of a discrete number of sharply defined bounded species.
If such species exist, one would expect a contribution from non-hydrogen-bonded
OH groups of H 2 O molecules near the corresponding OH-vibration mode of water
vapor (see Fig. 2.13). However, this was not observed. Moreover, the large dielectric
constant, (0), of water and ice implies strong molecular correlations and a high
polarization ability. These two mechanisms cannot be simultaneously satisfied in
terms of a hydrogen-bonded network of identical long-lived molecular species.
Although some aspects of the complex phenomenon of hydrogen bonding are
still suitable for the description of proton transfer, in general, it is outdated and
does not fully reflect modern spectroscopic data. The dynamics of hydrogen bonds
and Bernal–Fowler water (see Chap. 1) is probably not the best platform for the
analysis of the electrodynamics of water and ice. The concept of molecular water
was developed on the basis of diffusion-averaged dynamics and does not include
short-term (picosecond) high-frequency dynamics, i.e., high-frequency dynamics
assume additional to H 2 O short-lived species [10]. In Sects. 4.2 and 4.3 we discuss
a phenomenological model (the ionic model) of water, in which a variety of specific
bonds of well-defined molecular species are substituted with the simple electrostatic
interaction between the variety of short-lived ions and molecules. Although the ionic
model is yet to be tested and recognized, it looks promising for the explanation of
the anomalous properties of water beyond the electrodynamic data.
4.2 A Phenomenological Model for the Broadband
Dielectric Response
4.2.1 Microscopic Features of Self-diffusion
Frenkel showed [11] that molecules of a liquid undergo Brownian diffusion, being at
the same time in an oscillatory state similar to that in solids. In this way, he reduced
the theoretical gap between solids and liquids, allowing them to be considered on
the same footing. Figure 4.1 shows a snapshot of the relative arrangement of water
molecules estimated by neutron and X-ray diffraction techniques (see Sect. 1.2.3 for