10.5 Examples
We have selected two examples: (i) QTAIM study on the AgVO 3 , for the simulation of Ag nucleation and formation on AgVO 3 provoked in this crystal by the
electron-beam irradiation. (ii) An ELF and Thom’s catastrophe theory (BET) study
for different reaction pathways associated with the decomposition of glycolic acid
decomposition.
10.5.1 AgVO 3
Silver vanadium oxide nanomaterials such as AgVO 3 , have attracted extensive
attention owing to their potential applications in rechargeable high-energy density
lithium batteries [155] and sensors [156]. AgVO 3 has scarcely been studied in
morphologies, but two phases α-AgVO 3 and β-AgVO 3 are known. Both structures
are monoclinic and α-AgVO 3 is irreversibly transformed into β-AgVO 3 at around
200 °C [157]. β-AgVO 3 demonstrates a narrowband gap fit for visible light,
showing a high potential as an effective photocatalyst. However, the photocatalytic
activity of β-AgVO 3 is still insignificant because of its low capability to separate
electro-hole pairs, which significantly limits its practical extensive application.
Thus, further study is necessary to enhance its photo-catalytic performance for the
practical application. Recently, experimental and theoretical studies have reported
that surface modification such as Ag nanoparticles (with excellent conductivity and
strong electron trapping ability) on surfaces could enhance the separation rate of
photogenerated holes and electrons [158–160].
This investigation’s motivation essentially arises from a discovery of an
unwanted real-time in situ nucleation and growth of Ag filaments on α-Ag 2 WO 4 ,
Ag 3 PO 4 , and Ag 2 MoO 4 crystals which was driven by an accelerated electron beam
from an electronic microscope under high vacuum [161–165].
First-principles total-energy calculations were carried out within the periodic DFT
framework using the VASP program [166]. In the calculations, electrons were introduced one by one up to four in the monoclinic unit cells of α-AgVO 3 and β-AgVO 3 and
the distribution of these extra electrons takes place by means of a simultaneously
geometry optimization on both the lattice parameters and the atomic positions. The
Kohn-Sham equations have been solved by means of the Perdew, Burke, and
Ernzerhof exchange-correlation functional, and the electron-ion interaction described
by the projector-augmented-wave pseudopotentials [167, 168]. The plane-wave
expansion was truncated at a cut-off energy of 520 eV and the Brillouin zones have been
sampled through Monkhorst-Pack special k-points grids that assure geometrical and
energetic convergence for the AgVO 3 structures considered in this work.
A graphical representation of α-AgVO 3 and β-AgVO 3 structures using polyhedra is presented in Fig. 10.1a, b, respectively. The number of oxygen atoms
coordinating to a vanadium atom in α-AgVO 3 is four while that of β-AgVO 3 is five.
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J. Andrés et al.
We have selected two examples: (i) QTAIM study on the AgVO 3 , for the simulation of Ag nucleation and formation on AgVO 3 provoked in this crystal by the
electron-beam irradiation. (ii) An ELF and Thom’s catastrophe theory (BET) study
for different reaction pathways associated with the decomposition of glycolic acid
decomposition.
10.5.1 AgVO 3
Silver vanadium oxide nanomaterials such as AgVO 3 , have attracted extensive
attention owing to their potential applications in rechargeable high-energy density
lithium batteries [155] and sensors [156]. AgVO 3 has scarcely been studied in
morphologies, but two phases α-AgVO 3 and β-AgVO 3 are known. Both structures
are monoclinic and α-AgVO 3 is irreversibly transformed into β-AgVO 3 at around
200 °C [157]. β-AgVO 3 demonstrates a narrowband gap fit for visible light,
showing a high potential as an effective photocatalyst. However, the photocatalytic
activity of β-AgVO 3 is still insignificant because of its low capability to separate
electro-hole pairs, which significantly limits its practical extensive application.
Thus, further study is necessary to enhance its photo-catalytic performance for the
practical application. Recently, experimental and theoretical studies have reported
that surface modification such as Ag nanoparticles (with excellent conductivity and
strong electron trapping ability) on surfaces could enhance the separation rate of
photogenerated holes and electrons [158–160].
This investigation’s motivation essentially arises from a discovery of an
unwanted real-time in situ nucleation and growth of Ag filaments on α-Ag 2 WO 4 ,
Ag 3 PO 4 , and Ag 2 MoO 4 crystals which was driven by an accelerated electron beam
from an electronic microscope under high vacuum [161–165].
First-principles total-energy calculations were carried out within the periodic DFT
framework using the VASP program [166]. In the calculations, electrons were introduced one by one up to four in the monoclinic unit cells of α-AgVO 3 and β-AgVO 3 and
the distribution of these extra electrons takes place by means of a simultaneously
geometry optimization on both the lattice parameters and the atomic positions. The
Kohn-Sham equations have been solved by means of the Perdew, Burke, and
Ernzerhof exchange-correlation functional, and the electron-ion interaction described
by the projector-augmented-wave pseudopotentials [167, 168]. The plane-wave
expansion was truncated at a cut-off energy of 520 eV and the Brillouin zones have been
sampled through Monkhorst-Pack special k-points grids that assure geometrical and
energetic convergence for the AgVO 3 structures considered in this work.
A graphical representation of α-AgVO 3 and β-AgVO 3 structures using polyhedra is presented in Fig. 10.1a, b, respectively. The number of oxygen atoms
coordinating to a vanadium atom in α-AgVO 3 is four while that of β-AgVO 3 is five.
264
J. Andrés et al.