Evidence for the existence of directional repulsion effects by lone valence electron pairs and .pi. bonds in trigonal-bipyramidal molecules

1981 ◽  
Vol 20 (1) ◽  
pp. 296-297 ◽  
Author(s):  
K. O. Christe ◽  
H. Oberhammer
Keyword(s):  
Valence Electron ◽  
Electron Pairs ◽  
Trigonal Bipyramidal ◽  
Pi Bonds

Theoretical Calculation of the Polytypism Transition Temperature of Titanium Alloys on the Valence Electron Level

2012 ◽  
Vol 152-154 ◽  
pp. 342-347
Author(s):  
Hua Qu ◽  
Wei Dong Liu
Keyword(s):  
Transition Temperature ◽  
Titanium Alloys ◽  
Valence Electron ◽  
Pure Titanium ◽  
Electron Theory ◽  
Electron Level ◽  
Valence Electron Structure ◽  
Electron Pairs ◽  
Stable Element ◽  
Empirical Electron Theory

Based on the polytypism transition temperature(PPT) of pure titanium, the the empirical electron theory of solids and molecules(EET) and the basic theory of the phase transformation of titanium alloys, a new method to calculate the PTT of titanium alloys is put forward after calculating the valence electron structure(VES) parameter nA which is the covalence electron pairs on the strongest bond of alloy phases, the crystal cell weight of  and  phases in the structure, the compensation coefficient of the phase and the temperature coefficient of  stable element. After calculating the PTT of some common titanium alloys, we find that the theoretical values are consistent with the experimental ones, so it is feasible to calculate the polytypism transition temperature of the titanium alloys on the covalence electron level.

The modulated structure of the calcium aluminate Ca6(AlO2)12·Bi2O3

2010 ◽  
Vol 66 (6) ◽  
pp. 585-593 ◽  
Author(s):  
O. Pérez ◽  
S. Malo ◽  
M. Hervieu
Keyword(s):  
Single Crystal ◽  
Calcium Aluminate ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Electron Pairs ◽  
Modulated Structure ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Superspace Formalism ◽  
Single Crystal Analysis

Bismuth calcium aluminate, Bi2Ca6Al12O27, has been prepared as a ceramic and a single crystal. Analysis of reciprocal space using both electron and X-ray diffraction show an R-centred hexagonal unit cell: a = b = 17.3892 (4), c = 6.986 (1) Å. Additional weak reflections are observed; they require the introduction of a modulation wavevector q = 0.0453 (2)c* for indexing. The modulated structure has been solved using the superspace formalism [superspace group X\overline{3}(00\gamma)0]. A framework of corner-sharing AlO4 tetrahedra forms corrugated sixfold rings and uncommon triple rings. The Ca2+ cations exhibit an eightfold coordination sphere; edge-sharing CaO8 polyhedra form intertwinned zigzagging rows along c creating a three-dimensional net. Bi atoms are located in large hexagonal tunnels parallel to c and form Bi2O3 pairs, which adopt a trigonal bipyramidal configuration. The 6s 2 lone-electron pairs (Lp) point along c, in the opposite direction to the three Bi—O strong bonds to form two BiO3Lp tetrahedra with a common base. Different orientations of the Bi2O3Lp2 pairs, rotated by 60° around c, are observed. Their stacking modes in each of the hexagonal tunnels are described. The sequence of the stacking varies along c in each of the tunnels.

Influence of Micro-Addition Chromium on the Valence Electron Structure and Toughness of Fe2B Phase

2010 ◽  
Vol 34-35 ◽  
pp. 1135-1139
Author(s):  
Rui Na Ma ◽  
Yong Zhe Fan ◽  
Xiao Ming Cao ◽  
Ming Wen
Keyword(s):  
Fracture Toughness ◽  
Valence Electron ◽  
Chromium Content ◽  
Electron Structure ◽  
Valence Electron Structure ◽  
Electron Pairs ◽  
Good Corrosion Resistance ◽  
Length Difference ◽  
Fe2b Phase ◽  
Good Agreement

Fe2B is a kind of typical intermetallic compound, which has good corrosion resistance in molten zinc. However, the fatal intrinsic brittleness limits its further application in the Hot-Dip Galvanizing Industry. Therefore, it is worthwhile to improve the toughness of Fe2B phase. In this study, the fracture toughness property of Fe2B phase with and without micro-addition chromium is investigated. In comparison with pure Fe2B phase, the intrinsic brittleness of Fe2B phase with chromium is lower. In addition, the valence electron structure of Fe2B containing various chromium content is calculated by the method of bond length difference (BLD). The results show that, in the (Fe1-x Crx)2B phase, the number of covalent electron pairs and the weaker bond energy are increased by the substituting atom-Cr. The calculated results are in good agreement with experimental observations.

On the Structure of the [XeOF5]- Anion and of Heptacoordinated Complex Fluorides Containing One or Two Highly Repulsive Ligands or Sterically Active Free Valence Electron Pairs

1995 ◽  
Vol 34 (7) ◽  
pp. 1868-1874 ◽  
Author(s):  
Karl O. Christe ◽  
David A. Dixon ◽  
Jeremy C. P. Sanders ◽  
Gary J. Schrobilgen ◽  
Scott S. Tsai ◽  
...  
Keyword(s):  
Valence Electron ◽  
Free Valence ◽  
Electron Pairs ◽  
Complex Fluorides

scholarly journals Synthesis and crystal structure of [Cs([2.2.2]crypt)]2[Mo(CO)5]

IUCrData ◽  
2019 ◽  
Vol 4 (9) ◽  
Author(s):  
Marina Kaas ◽  
Nikolaus Korber
Keyword(s):  
Triple Bond ◽  
Valence Electron ◽  
Liquid Ammonia ◽  
Metal Carbonyl ◽  
Carbonyl Complex ◽  
Anionic Complex ◽  
Synthesis And Crystal Structure ◽  
Carbonyl Ligands ◽  
Trigonal Bipyramidal ◽  
Metallic Salt

Reduction of the heteroleptic metal carbonyl complex Mo(CO)3(η5-Cp)H with the metallic salt Cs5Bi4 in the presence of [2.2.2]crypt (= 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) in liquid ammonia led to single crystals of bis[(4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)caesium] pentacarbonylmolybdate, [Cs(C18H36N2O6)]2[Mo(CO)5] or [Cs([2.2.2]crypt)]2[Mo(CO)5]. The twofold negatively charged anionic complex corresponds to the 18 valence electron rule. It consists of an Mo atom coordinated by five carbonyl ligands in a shape intermediate between trigonal–bipyramidal and square-pyramidal. The Mo—C distances range from 1.961 (3) to 2.017 (3) Å, and the C[triple-bond]O distances from 1.164 (3) to 1.180 (4) Å.

Band-Resolved Double Photoemission Spectroscopy on Correlated Valence Electron Pairs in Metals

2017 ◽  
Vol 118 (13) ◽  
Author(s):  
Andreas Trützschler ◽  
Michael Huth ◽  
Cheng-Tien Chiang ◽  
Robin Kamrla ◽  
Frank O. Schumann ◽  
...  
Keyword(s):  
Valence Electron ◽  
Photoemission Spectroscopy ◽  
Electron Pairs

BOND LENGTHS AND BOND ANGLES IN OCTAHEDRAL, TRIGONAL- BIPYRAMIDAL, AND RELATED MOLECULES OF THE NON-TRANSITION ELEMENTS

1961 ◽  
Vol 39 (2) ◽  
pp. 318-323 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Central Atom ◽  
Lone Pair ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
Transition Elements ◽  
Electron Pairs ◽  
Bond Angles ◽  
Bond Lengths ◽  
Trigonal Bipyramidal ◽  
The Difference

The stereochemistry of molecules in which there are five or six pairs of electrons in the valency shell of a central atom is discussed in terms of the repulsions that exist between pairs of electrons in the valency shell as a consequence of the operation of the Pauli exclusion principle. An explanation is given for the difference in lengths of the axial and equatorial bonds in molecules such as PCl5 and ClF3 whose structures are based on the trigonal-bipyramidal arrangement of five valency-shell electron pairs. The fact that in molecules with a central atom with a valency shell of six electron pairs, one of which is a lone pair and which have the structure of a square pyramid, the central atom always lies below rather than in, or above, the base of the square pyramid, is also accounted for.

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