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Valence (chemistry)

About: Valence (chemistry) is a research topic. Over the lifetime, 24937 publications have been published within this topic receiving 645252 citations. The topic is also known as: valency.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the homogeneous substitution of O by N in the whole particles of layered titanates was reported, and the resultant materials Cs0.68Ti1.83O4−xNx exhibited extraordinary band-to-band excitation in the visible-light ranging up to blue light.
Abstract: The distribution of dopants in semiconductors can intrinsically determine the electronic structure and consequently the absorbance, redox potential, and charge-carrier mobility of the semiconductor photocatalysts. In contrast to most reported nitrogen-doped titania photocatalysts with some localized states in the intrinsic band gap and small visible light absorption shoulders induced by inhomogeneous nitrogen doping near the particle surface, we report here the homogeneous substitution of O by N in the whole particles of layered titanates. The resultant materials Cs0.68Ti1.83O4−xNx exhibited extraordinary band-to-band excitation in the visible-light ranging up to blue light. From photoelectron spectroscopy and first-principles calculations, the upward shift of valence band maximum by N 2p states is concluded as the cause of the band-to-band visible light excitation. The holes generated upon visible light excitation in the newly formed valence bands of Cs0.68Ti1.83O4−xNx and H0.68Ti1.83O4−xNx had strong ox...

282 citations

Journal ArticleDOI
TL;DR: The participation of 4f electrons in the bonding of the lanthanide complexes Ln(NR2)3; R = H, SiH3, has been investigated at the DFT level as mentioned in this paper.
Abstract: The participation of 4f electrons in the bonding of the lanthanide complexes Ln(NR2)3; R = H, SiH3, has been investigated at the DFT level. Structural parameters obtained with small core (f electrons in the valence) and large core (f electrons in the core) effective core potentials (ECPs) suggest the nonparticipation of the f electrons to the Ln−N bonding. A methodological study has been carried out on the lanthanide contraction with various ab initio methods using large core ECPs. The calculated lanthanide contraction (0.180 A) is in excellent agreement with the experimental value (0.179 A). Comparison of calculated structural parameters with available X-ray data shows that calculations with large core ECPs and density functional methods quantitatively reproduce the bonding at the lanthanide.

282 citations

Book ChapterDOI
01 Jan 1992
TL;DR: In this paper, the Inverse trans influence is introduced in the context of the actinide-oxygen bond and the experimental energy level scheme is compared with the results of molecular orbital calculations of varying degrees of sophistication, the most successful being SCF calculations incorporating the effects of relativity.
Abstract: The actinyl ions exhibit an unusually robust covalent bond which has a profound influence on their chemistry. Their electronic structure has been unravelled by the use of a variety of optical measurements and by photoelectron spectroscopy, which together establish the composition and role of the valence orbitals. The experimental energy level scheme can be compared with the results of molecular orbital calculations of varying degrees of sophistication, the most successful being SCF calculations incorporating the effects of relativity. An important contribution to the bonding comes from the pseudo-core 6p shell, which is important in determining the linearity of the ions. A new concept, the Inverse trans Influence, is introduced in this context. There is some evidence that (d-orbital π-bonding is more important than σ-bonding. The remarkable strength of the actinyl bond can be attributed to the presence in the valence shell of both f and d metal orbitals, giving each actinide-oxygen bond a formal bond order of three.

281 citations

Journal ArticleDOI
TL;DR: In this article, the main structural cause of ferroelectricity in Bi4Ti3O12 and Bi3TiNbO9 is shown to be the a-axis displacement of Bi atoms in the perovskite A sites with respect to the chains of TiO6 octahedra.

280 citations

Journal ArticleDOI
TL;DR: In this article, partial third-order (P3) quasiparticle approximation of the electron propagator has an average absolute error of 0.19 eV for benzene and borazine spectra.
Abstract: Valence ionization energies of a set closed‐shell molecules calculated in a partial third‐order (P3) quasiparticle approximation of the electron propagator have an average absolute error of 0.19 eV. Diagonal elements of the self‐energy matrix include all second‐order and some third‐order self‐energy diagrams. Because of its fifth power dependence on basis set size and its independence from electron repulsion integrals with four virtual indices, this method has considerable potential for large molecules. Formal and computational comparisons with other electron propagator techniques illustrate the advantages of the P3 procedure. Additional applications to benzene and borazine display the efficacy of the P3 propagator in assigning photoelectron spectra. In the borazine spectrum, 2E′ and 2A2′ final states are responsible for an observed feature at 14.76 eV. Another peak at 17.47 eV is assigned to a 2E′ final state.

280 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,521
20222,997
2021616
2020611
2019584
2018577