1.1 Overview
9
reduction in fuel cells [103–105]. Carbon-based metal-free catalysts with heterocoordinated doped atoms have been demonstrated to be effective for an increasing
number of catalytic processes [103]. The combination of the ultralow coordination
and hetero-coordination results in the unexpectedly strong quantum entrapment of
the core electrons and polarization of the dangling bond electrons, which stems the
catalytic ability of the metal-free substance [2].
As the wall materials in a fusion device, Be/W alloy protects efficiently nuclear
radiation in the International Thermonuclear Experimental Reactor (ITER) [106–
110]. Due to the electronic structure difference between W and Be, a strong influence
of alloying on both the core and the valence electrons and the interfacial energy may
happen but the verification and quantification of this expectation remains unrealistic.
Understanding the nature of the bond and the behavior of the energetic electrons at
the alloying interface is crucial to designing such functional materials for nuclear
radiation protection and catalysis application, particularly.
Therefore, experimental distillation of the atomistic, local, dynamic, and quantitative information and theoretical clarification of the physical origin about the
bonding and electronic dynamics at the irregularly coordinated atomic site are of
paramount importance to advancing the subjects of Hetero-coordination Chemistry
and Undercoordination Physics.
1.1.2 Challenges Faced by Existing Probing Technologies
Formation of bonds between hetero-coordinated atoms and relaxation of bonds
between undercoordinated atoms and the associated electron entrapment and polarization mediate the performance of a substance at these irregularly-coordinated
atomic sites [1]. However, resolving such atomistic, dynamic, local, and quantitative information is beyond the scope of available techniques though the invention
of STM/S has advanced surface science enormously. STM/S maps electrons of the
outermost layer of atoms within the energy window of a few eVs crossing E F [111].
For instances, atomic vacancies at a graphite(0001) skin [42] and at the zigzag edge
of a graphene exhibit the same topological and the same Fermi resonant signatures
[112]. The resonant states, named Dirac Fermions, serve as carriers for topological insulators exhibiting the anomalous quantum Hall effect [33, 110]. The Dirac
Fermions are almost massless with nonzero spin and infinitely large group velocity.
STM also probed the “check-board” like protrusions from Cu(100)–O
− surface
[113]. The “check-board” protrusions evolve subsequently into the “dumb-bell” like
protrusions when the O
− adsorbate transits into the O
2− [114]. The latter exhibits
the characteristic antibonding density of states (DOS) featured at +2.0 eV above E F
and the nonbonding states at −2.1 eV below [115]. The former corresponds to the
polarization of the Cu
p dipoles by the O
− and the latter to the Cu
p dipoles by the
electron lone pair of the O
2− [45].
STM/S probed the volume expansion and electron polarization for Au atoms at
ends of the monatomic chain [52], for Ag atoms added on Ag(111) skin [116], and
9
reduction in fuel cells [103–105]. Carbon-based metal-free catalysts with heterocoordinated doped atoms have been demonstrated to be effective for an increasing
number of catalytic processes [103]. The combination of the ultralow coordination
and hetero-coordination results in the unexpectedly strong quantum entrapment of
the core electrons and polarization of the dangling bond electrons, which stems the
catalytic ability of the metal-free substance [2].
As the wall materials in a fusion device, Be/W alloy protects efficiently nuclear
radiation in the International Thermonuclear Experimental Reactor (ITER) [106–
110]. Due to the electronic structure difference between W and Be, a strong influence
of alloying on both the core and the valence electrons and the interfacial energy may
happen but the verification and quantification of this expectation remains unrealistic.
Understanding the nature of the bond and the behavior of the energetic electrons at
the alloying interface is crucial to designing such functional materials for nuclear
radiation protection and catalysis application, particularly.
Therefore, experimental distillation of the atomistic, local, dynamic, and quantitative information and theoretical clarification of the physical origin about the
bonding and electronic dynamics at the irregularly coordinated atomic site are of
paramount importance to advancing the subjects of Hetero-coordination Chemistry
and Undercoordination Physics.
1.1.2 Challenges Faced by Existing Probing Technologies
Formation of bonds between hetero-coordinated atoms and relaxation of bonds
between undercoordinated atoms and the associated electron entrapment and polarization mediate the performance of a substance at these irregularly-coordinated
atomic sites [1]. However, resolving such atomistic, dynamic, local, and quantitative information is beyond the scope of available techniques though the invention
of STM/S has advanced surface science enormously. STM/S maps electrons of the
outermost layer of atoms within the energy window of a few eVs crossing E F [111].
For instances, atomic vacancies at a graphite(0001) skin [42] and at the zigzag edge
of a graphene exhibit the same topological and the same Fermi resonant signatures
[112]. The resonant states, named Dirac Fermions, serve as carriers for topological insulators exhibiting the anomalous quantum Hall effect [33, 110]. The Dirac
Fermions are almost massless with nonzero spin and infinitely large group velocity.
STM also probed the “check-board” like protrusions from Cu(100)–O
− surface
[113]. The “check-board” protrusions evolve subsequently into the “dumb-bell” like
protrusions when the O
− adsorbate transits into the O
2− [114]. The latter exhibits
the characteristic antibonding density of states (DOS) featured at +2.0 eV above E F
and the nonbonding states at −2.1 eV below [115]. The former corresponds to the
polarization of the Cu
p dipoles by the O
− and the latter to the Cu
p dipoles by the
electron lone pair of the O
2− [45].
STM/S probed the volume expansion and electron polarization for Au atoms at
ends of the monatomic chain [52], for Ag atoms added on Ag(111) skin [116], and