1.2 Bragg Scattering and Bernal–Fowler Water
5
z
x
y
p x
p x
-
-
+
+
p z +p y
s
p z +p y
Electrons
Protons
Fig. 1.2 The electron and nuclei distribution in a water molecule according to the Bernal–Fowler
model. Adapted from [9], with the permission of AIP Publishing
Fig. 1.3 a The schematic of X-ray experiments with water. b X-ray diffraction intensity-angle
distributions for water (curve 1); theoretical pattern for a quartz-like water model (curve 2); and the
theoretical pattern for amorphous quartz (curve 3). Adapted from [9], with the permission of AIP
Publishing
high mobility of H
+ and OH
− ions,
4 which assumes something other than the simple
hydration of ionic species, a mechanism that allows H
+ and OH
− ions to move
through the media and impart coherence.
Therefore, a number of modifications to the Bernal–Fowler water model were later
proposed. For example, Fig. 1.5 assembles the main species that different models
introduced to the quartz-like water model in order to interpret the scope of electrodiffusion data. Defects of different types can be found: vacancies, interstitials, chains,
excess protons, holes, free, and randomly bounded molecules. All these particles were
needed to provide additional degrees of freedom to the static lattice structure revealed
4 The electrical mobility of H 3 O + and OH − ions is known to be almost an order of magnitude larger
than the mobility of other ions with the same charge such as Li + , Na + , and K + [11]. This point
was later understood by the Grotthuss mechanism (see Sect. 1.3).
5
z
x
y
p x
p x
-
-
+
+
p z +p y
s
p z +p y
Electrons
Protons
Fig. 1.2 The electron and nuclei distribution in a water molecule according to the Bernal–Fowler
model. Adapted from [9], with the permission of AIP Publishing
Fig. 1.3 a The schematic of X-ray experiments with water. b X-ray diffraction intensity-angle
distributions for water (curve 1); theoretical pattern for a quartz-like water model (curve 2); and the
theoretical pattern for amorphous quartz (curve 3). Adapted from [9], with the permission of AIP
Publishing
high mobility of H
+ and OH
− ions,
4 which assumes something other than the simple
hydration of ionic species, a mechanism that allows H
+ and OH
− ions to move
through the media and impart coherence.
Therefore, a number of modifications to the Bernal–Fowler water model were later
proposed. For example, Fig. 1.5 assembles the main species that different models
introduced to the quartz-like water model in order to interpret the scope of electrodiffusion data. Defects of different types can be found: vacancies, interstitials, chains,
excess protons, holes, free, and randomly bounded molecules. All these particles were
needed to provide additional degrees of freedom to the static lattice structure revealed
4 The electrical mobility of H 3 O + and OH − ions is known to be almost an order of magnitude larger
than the mobility of other ions with the same charge such as Li + , Na + , and K + [11]. This point
was later understood by the Grotthuss mechanism (see Sect. 1.3).