Influence of pressure on the valence bond structure of tungsten

2007 ◽  
Vol 394 (1) ◽  
pp. 27-32
Author(s):  
Xiaobo Li ◽  
Youqing Xie ◽  
Yaozhuang Nie ◽  
Hongjian Peng
Keyword(s):  
Valence Bond ◽  
Valence Bond Structure

Valence Bond Structure and Mechanical Properties of CNxFilms Prepared by Glow Discharge Assisted Pulsed Laser Deposition

2013 ◽  
Vol 40 (11) ◽  
pp. 1107002
Author(s):  
郑晓华 Zheng Xiaohua ◽  
宋建强 Song Jianqiang ◽  
杨芳儿 Yang Fanger ◽  
陈占领 Chen Zhanling
Keyword(s):  
Mechanical Properties ◽  
Glow Discharge ◽  
Pulsed Laser Deposition ◽  
Valence Bond ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Valence Bond Structure

Temperature-dependent valence bond structure study of tantalum

2007 ◽  
Vol 393 (1-2) ◽  
pp. 119-124 ◽  
Author(s):  
Li Xiaobo ◽  
Xie Youqing ◽  
Nie Yaozhuang ◽  
Peng Hongjian
Keyword(s):  
Valence Bond ◽  
Structure Study ◽  
Temperature Dependent ◽  
Valence Bond Structure

Valence Bond Studies of N5+

2002 ◽  
Vol 57 (9) ◽  
pp. 983-992 ◽  
Author(s):  
Richard D. Harcourta ◽  
Thomas M. Klapötkeb
Keyword(s):  
Valence Bond ◽  
Molecular Orbital Calculations ◽  
Energy Minimum ◽  
Localized Molecular Orbitals ◽  
Bond Lengths ◽  
Formal Charge ◽  
Valence Structure ◽  
Valence Bond Structure ◽  
Lewis Structures ◽  
Increased Valence

The results of STO-6G valence-bond studies are reported for the six π-electrons of C2v symmetry N5+, with π-electron core charges determined from the valence bond structures. Important types of canonical Lewis structures are calculated to carry either three atomic formal charges, arranged spatially as (+), (-) and (+) , as in or a single (+) atomic formal charge, as in the “long-bond” structure When localized molecular orbitals are used to accommodate bonding electrons between pairs of adjacent atoms, each of these types of Lewis structures, and others, are components of the increased-valence structure whose bond properties are in qualitative accord with experimental estimates of the bond lengths for N5+. Consideration is also given to other types of valence bond representations for N5+, and the results of MP2 molecular orbital calculations for the hypothetical N82+ are reported. For the latter species, a stable energy minimum with C2 symmetry is obtained. Its bond lengths are related to those implied by a Lewis-type valence-bond structure

The negative 7J(CHO, CH3) in 4-methylbenzaldehyde. Ionicity of the carbonyl bond

1992 ◽  
Vol 70 (10) ◽  
pp. 2555-2557
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
First Principles ◽  
Valence Bond ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Unexpected Result ◽  
Coupling Constant ◽  
Valence Bond Structure ◽  
Carbonyl Bond ◽  
Spin Spin Coupling ◽  
Benzaldehyde Derivatives

The spin–spin coupling constant over seven bonds between the formyl and methyl protons in 4-methylbenzaldehyde is −0.030 Hz in CS2/C6D12/TMS, and (−)0.035 Hz in acetone-d6, solutions at 297 K. This unexpected result is rationalized in terms of a spin–spin coupling mechanism attributed to the importance of a valence bond structure with an ionic carbonyl bond. The result again emphasizes the sensitivity to substituent perturbations of the six-bond coupling constant in quasi-planar benzaldehyde derivatives. It can have either sign and presents a challenge to its computation from first principles.

Valence bond structure of Ta-W alloys

2009 ◽  
Vol 22 (4) ◽  
pp. 275-283 ◽  
Author(s):  
Xiaobo LI ◽  
Youqing XIE
Keyword(s):  
Valence Bond ◽  
Valence Bond Structure

Three-electron bonds and a valence-bond study of the rotation barrier for N2O4

1978 ◽  
Vol 31 (8) ◽  
pp. 1635 ◽  
Author(s):  
RD Harcourt
Keyword(s):  
Molecular Orbital ◽  
Significant Contribution ◽  
Valence Bond ◽  
Rotation Barrier ◽  
Atomic Orbitals ◽  
Planar Conformation ◽  
Valence Bond Structure ◽  
Oxygen Atoms

From molecular orbital studies, a number of previous workers have concluded that a most significant contribution to the barrier to rotation around the NN bond of N2O4 arises from the overlap of pairs of atomic orbitals located on the cis oxygen atoms of the planar conformation. A valence-bond study of this overlap contribution is reported. It is calculated that the 'long OO bond' formed by overlap of singly occupied 2pπ-orbitals in the valence-bond structure (3) for the planar conformation has negligible strength, and that insufficient stabilization is obtained when this structure participates in resonance with ionic structures of the type (5a). Diagram The primary overlap stabilization for the planar conformation is calculated to arise from resonance between structures of the types (2a) and (7). The O. :O ↔ 0: .O resonance that pertains here is equivalent to the formation of a Pauling 'three-electron bond' O...O between the two atoms. Therefore, the development of this type of bond in the planar conformation can be associated with the cis OO overlap contribution to the barrier to rotation around the NN bond. Another type of Pauling three-electron bond resonance, namely (4) ↔ (6), is calculated to produce a smaller but not insignificant stabilization of the planar conformation.

Sign in / Sign up

Export Citation Format

Share Document