Metavalent Bonding Origins of Unusual Properties of Group IV Chalcogenides
35
Citation
38
Reference
10
Related Paper
Citation Trend
Abstract:
A distinct type of metavalent bonding (MVB) is recently proposed to explain an unusual combination of anomalous functional properties of group IV chalcogenide crystals, whose electronic mechanisms and origin remain controversial. Through theoretical analysis of evolution of bonding along continuous paths in structural and chemical composition space, emergence of MVB in rocksalt chalcogenides is demonstrated as a consequence of weakly broken symmetry of parent simple-cubic crystals of Group V metalloids. High electronic degeneracy at the nested Fermi surface of parent metal drives spontaneous breaking of its translational symmetry with structural and chemical fields, which open up a small energy gap and mediate strong coupling between conduction and valence bands making metavalent crystals highly polarizable, conductive, and sensitive to bond-lengths. Stronger symmetry-breaking structural and chemical fields, however, transform them discontinuously to covalent and ionic semiconducting states. MVB involves bonding-antibonding pairwise interactions alternating along linear chains of at least five atoms, which facilitate long-range electron transfer in response to polar fields causing unusual properties. The precise picture of MVB predicts anomalous second-order Raman scattering as an addition to set off their unusual properties, and will guide in design of new metavalent materials with improved thermoelectric, ferroelectric and nontrivial electronic topological properties.Keywords:
Antibonding molecular orbital
Cite
Citations (0)
Network covalent bonding
Morse potential
Bond cleavage
Mechanochemistry
Cite
Citations (8)
Bonding in solids
Atoms in molecules
Cite
Citations (0)
In this paper, the bond energy of some covalent molecules has been calculated with IEHM. The relations of the bond energy and chemical properties such as stability, acidity, chemical reaction rate, substituted orientation law and hyper - conjugation effect are further studied.
Bond energy
Characterization
Sextuple bond
Chemical Stability
Cite
Citations (2)
The electronic structure and the chemical bonding mechanism of silver oxide are studied on the basis of band-structure calculations, using the full-potential linearized augmented-plane-wave (FLAPW) method. Our calculations indicate that silver oxide is a metal (or a semi-metal). Total and partial densities of states and electron densities were calculated and are utilized to give an interpretation of the chemical bonding. The admixture of the Ag 5s states with the Ag 4d-O 2p bands proved to be essential for the covalent bonding effect, since pure 4d-2p bands, with bonding and antibonding states fully occupied, do not lead to a covalent energy gain. It is found that there are significant deviations from a simple ionic picture due to the depletion of the valence band of the Ag 4d electrons, leading to non-spherical charge density around the silver.
Antibonding molecular orbital
Silver oxide
Density of states
Charge density
Cite
Citations (19)
Abstract We studied characteristics of chemical bond and vacancy formation in chalcopyrite‐type CuInSe 2 (CIS) by first principles calculations. The chalcopyrite‐type CIS has two kinds of chemical bonds, Cu‐Se and In‐Se. The Cu‐Se bond is a weak covalent bonding because electrons occupy both bonding and antibonding orbitals of Cu 3d and Se 4p and occupy only the bonding orbital (a 1 ) of Cu 4s and Se 4p and do not occupy the antibonding orbital (a 1 * ) of Cu 4s and Se 4p. On the other hand, the In‐Se bond has a partially covalent and partially ionic character because the In 5s orbital covalently interacts with Se 4p; the In 5p orbital is higher than Se 4p and so the electron in the In 5p orbital moves to the Se 4p orbital. The average bond order of the Cu‐Se and In‐Se bonds can be calculated to be 1/4 and 1, respectively. The bond order of Cu‐Se is smaller than that of In‐Se. The characteristics of these two chemical bonds are related to the formation of Cu and In vacancies in CIS. The formation energy of the Cu vacancy is smaller than that of the In vacancy under both Cu‐poor and In‐poor conditions. The displacement (Δ l ) of the surrounding Se atoms after the formation of the Cu vacancy is smaller than the Δ l after the formation of the In vacancy. The interesting and unique characteristics of CIS are discussed on the basis of the characteristics of the chemical bond. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Antibonding molecular orbital
Electron deficiency
Electron localization function
Bond energy
Cite
Citations (28)
Antibonding molecular orbital
Three-center two-electron bond
Molecular orbital diagram
Non-bonding orbital
Electron configuration
Metallic bonding
Cite
Citations (0)
Sextuple bond
Bent bond
Three-center two-electron bond
Quadruple bond
Single bond
Pi bond
Bond-dissociation energy
Cite
Citations (4)
A new electronegativity table of elements in covalent crystals with different bonding electrons and the most common coordination numbers is suggested on the basis of covalent potentials of atoms in crystals. For a given element, the electronegativity increases with increasing number of bonding electrons and decreases with increasing coordination number. Particularly, the ionicity of a covalent bond in different environments can be well-reflected by current electronegativity values; that is, the ionicity of chemical bonds increases as the coordination number of the bonded atoms increases. We show that this electronegativity scale can be successfully applied to predict the hardness of covalent and polar covalent crystals, which will be very useful for studying various chemical and physical properties of covalent materials.
Electronegativity
Network covalent bonding
Coordination number
Cite
Citations (49)
Solid-state physics
Ionic crystal
Cite
Citations (11)