The Contribution To Bond Valences By Lone Electron Pairs

2004 ◽  
Vol 848 ◽  
Author(s):  
Xiqu Wang ◽  
Friedrich Liebau
Keyword(s):  
Coordination Sphere ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Bond Valence ◽  
Alkali Cations ◽  
Continuous Increase ◽  
Electron Pairs ◽  
Effective Valence

ABSTRACTBond valence sums (BVS) calculated for lone-pair cations are found increasingly higher than their formal valences as the retraction of the lone electron pair (LEP) from the nucleus is more pronounced. The increase in BVS is interpreted as a continuous increase of an effective valence of an atom that is a measure of its actual ability to bind other atoms without changing its formal valence. How the LEP of a lone-pair cation affects the effective valence of other atoms in a structure is studied by bond valence calculations for specific structures. For structures rich in alkali cations, it is found that the high effective valence of the lone-pair cations tends to be balanced by low effective valence of alkali cations. The LEP transfers bonding power or effective valence from the alkali cations to the lone-pair cations by joining the coordination sphere of the alkali cations.

Studies on bond and atomic valences. I. correlation between bond valence and bond angles in SbIII chalcogen compounds: the influence of lone-electron pairs

1996 ◽  
Vol 52 (1) ◽  
pp. 7-15 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Statistical Analysis ◽  
Valence State ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Continuous Change ◽  
Oxidation Number ◽  
Electron Pairs ◽  
Atomic Valence ◽  
Bond Valence Parameter

In the present bond-valence concept the bond-valence parameter ro is treated as constant for a given pair of atoms, and it is assumed that the bond valence sij is a function of the corresponding bond length Dij , and that the atomic valence is an integer equal to the formal oxidation number for Vi derived from stoichiometry. However, from a statistical analysis of 76 [SbIIIS n ] and 14 [SbIIISe n ] polyhedra in experimentally determined structures, it is shown that for SbIII—X bonds (X = S, Se), ro is correlated with {\bar \alpha} i , the average of the X—Sb—X angles between the three shortest Sb—X bonds. This is interpreted as a consequence of a progressive retraction of the 5s lone-electron pair from the SbIII nucleus, which can be considered as continuous change of the actual atomic valence act Vi of Sb from +3 towards +5. A procedure is derived to calculate an effective atomic valence eff Vi of SbIII from the geometry, {\bar \alpha} i and Dij , of the [SbIII Xn ] polyhedra, which approximates act Vi and is a better description of the actual valence state of SbIII than the formal valence for Vi . Calculated eff V SbIII are found to vary between +2.88 and +3.80 v.u. for [SbIIIS n ] and between +2.98 and +3.88 v.u. for [SbIIISe n ] polyhedra. It is suggested that a corresponding modification of the present bond-valence concept is also required for other cations with lone-electron pairs.

scholarly journals Lone-pair effect on carrier capture in Cu2ZnSnS4solar cells

2019 ◽  
Vol 7 (6) ◽  
pp. 2686-2693 ◽  
Author(s):  
Sunghyun Kim ◽  
Ji-Sang Park ◽  
Samantha N. Hood ◽  
Aron Walsh
Keyword(s):  
Solar Cells ◽  
Fast Electron ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Electron Hole ◽  
Carrier Capture ◽  
Hole Recombination

Fast electron–hole recombination in kesterite solar cells is linked to the chemistry of the Sn lone electron pair.

Influence of polyhedron distortions on calculated bond-valence sums for cations with one lone electron pair

2007 ◽  
Vol 63 (2) ◽  
pp. 216-228 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Periodic System ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Correlation Equations ◽  
Coordination Polyhedra ◽  
Absolute Value ◽  
Whole Number ◽  
Correlation Parameters ◽  
Bond Valence Model

In the present bond-valence model (BVM), the bond-valence parameters r 0 and b are, in general, supposed to be constant for each A–X pair and equal to 0.37 Å for all A–X pairs, respectively. For [A i (X j ) n ] coordination polyhedra that do not deviate strongly from regularity, these suppositions are well fulfilled and calculated values for the bond-valence sums (BVS) i are nearly equal to the whole-number values of the stoichiometric valence. However, application of the BVM to 2591 [L i (X j ) n ] polyhedra, where L are p-block cations, i.e. cations of the 13th to 17th group of the periodic system of elements, with one lone electron pair and X = O−II, S−II and Se−II, shows that r 0i values of individual [LX n ] polyhedra are correlated with the absolute value |Φ i | of an eccentricity parameter, Φ i , which is higher for more distorted [LX n ] polyhedra. As a consequence, calculated (BVS) i values for these polyhedra are also correlated with |Φ i |, rather than being numerically equal to the stoichiometric valence of L. This is interpreted as the stereochemical influence of the lone electron pair of L. It is shown that the values of the correlation parameters and the R 2 values of the correlation equations depend on the position of the L cation in the periodic system of elements, if the correlations are assumed to be linear. This observation suggests that (BVS) L describes a chemical quantity that is different from the stoichiometric valence of L.

Structure of russellite (Bi2WO6): origin of ferroelectricity and the effect of the stereoactive lone electron pair on the structure

2018 ◽  
Vol 74 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Hiroki Okudera ◽  
Yuka Sakai ◽  
Kentaro Yamagata ◽  
Hiroaki Takeda
Keyword(s):  
Low Temperature ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Orthorhombic Phase ◽  
Electrostatic Charge ◽  
X Ray Diffraction ◽  
Coordination Environment ◽  
X Ray ◽  
Powder Neutron Diffraction

The structure of the low-temperature polar (orthorhombic) phase of russellite (Bi2WO6) was examined on artificial specimens with precise single-crystal X-ray diffraction experiments. The final atomic arrangement thus obtained was identical to that reported by Knight [Miner. Mag. (1992), 56, 399–409] with powder neutron diffraction. The residual density attributable to a stereochemically-active lone pair of electrons of bismuth was prominent at approximately the centre of a larger cap of BiO8 square antiprisms, that is on the line from the Bi sites to an adjacent WO4 2− slab along the b-axis direction. Quite uneven Bi—O distances and the formation of a vacant coordination hemisphere (within 3 Å) should, therefore, be ascribed to the strong demand of bismuth to form shorter Bi—O bonds to use up its electrostatic charge within its coordination environment. The shift of bismuth along −c propagates via the correlated shift of the W site and these cooperative shifts cause ferroelectricity in the compound. This propagation was easily effected by the intrusion of molecules such as acetone into the structure.

Spatial dispersion of lone electron pairs? – Experimental charge density of cubic arsenic(iii) oxide

2015 ◽  
Vol 17 (16) ◽  
pp. 11020-11027 ◽  
Author(s):  
Piotr A. Guńka ◽  
Zygmunt Gontarz ◽  
Janusz Zachara
Keyword(s):  
Charge Density ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Spatial Dispersion ◽  
Electron Pairs ◽  
First Time ◽  
Experimental Charge Density

Lone electron pair dispersion into three separate domains in space is reported and discussed for the first time.

Exploration of the α-effect by substitution on hydroxylamine anions. I. Effects of alkyl- and fluoroalkylation

2014 ◽  
Vol 92 (4) ◽  
pp. 346-353 ◽  
Author(s):  
D. Afzal ◽  
K.R. Fountain
Keyword(s):  
Oxygen Atom ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Electronic Effects ◽  
Important Indicator ◽  
Comprehensive Study ◽  
Simple Models

Many explanations for the α-effect have been suggested. Most are simple models conjecturing various sources affecting the nucleophilic behavior. This paper provides a comprehensive study of electronic effects using the single α-atom lone electron pair of substituted hydroxyl amine anions. This substituent scheme shows that the interaction of this lone pair with the negatively charged oxygen atom is an important indicator of reactivity.

scholarly journals On the correlations between the polyhedron eccentricity parameters and the bond-valence sums for the cations with one lone electron pair. Addendum

2009 ◽  
Vol 65 (3) ◽  
pp. 401-402 ◽  
Author(s):  
Vasyl Sidey
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Acta Cryst

Systematic variations of the bond-valence sums calculated from the poorly determined bond-valence parameters [Sidey (2008), Acta Cryst. B64, 515–518] have been illustrated using a simple graphical scheme.

The gauche effect on conformation. α-Substituted sulfones and N-substituted sulfonamides

1979 ◽  
Vol 44 (11) ◽  
pp. 3378-3384 ◽  
Author(s):  
Otto Exner ◽  
Jan B. F. N. Engberts
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Conformational Preference ◽  
Electron Pairs ◽  
Gauche Effect

The dipole moments of α-halogenosulfones IIa-f in benzene solution revealed the conformation C, those of N-methyl-N-nitrosulfonamides IIIa-c the conformation F. In either case the conformational preference is governed by the gauche rule which may be worded in a modified version that symmetrical positions of polar bonds and/or of lone electron pairs are disfavoured. A lone electron pair appears to be more significant than a polar bond.

Nonlinear optical ASnX (A = Na, H; X = N, P) nanosheets with divalent tin lone electron pair effect by first-principles design

Nanoscale ◽  
2020 ◽  
Vol 12 (27) ◽  
pp. 14895-14902
Author(s):  
Shengzi Zhang ◽  
Lei Kang ◽  
Zheshuai Lin
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
First Principles ◽  
Nonlinear Optical ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Second Harmonic ◽  
Electron Pairs ◽  
Divalent Tin

Divalent tin Sn2+ lone electron pairs can induce strong second harmonic generation density in 2D NaSnP and HSnN structures.

A comment on the structure of xenon hexafluoride

1978 ◽  
Vol 31 (9) ◽  
pp. 1917 ◽  
Author(s):  
DL Kepert
Keyword(s):  
Electron Pair ◽  
Lone Pair ◽  
Xenon Atom ◽  
Electron Pairs ◽  
Repulsion Energy ◽  
A Value ◽  
Bonding Electron

Calculations based on the minimization of the repulsion energy between electron pairs show that the structure of xenon hexafluoride is predicted if the non-bonding electron pair is situated close to the xenon atom. If a value of n = 6 is assumed in the repulsion law, the distance between the xenon atom and the effective centre of repulsion of the lone pair is approximately 10% of the distance between the xenon atom and the effective centres of repulsion of the bonding pairs.

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