scholarly journals Bond softness sensitive bond-valence parameters for crystal structure plausibility tests

IUCrJ ◽  
2017 ◽  
Vol 4 (5) ◽  
pp. 614-625 ◽  
Author(s):  
Haomin Chen ◽  
Stefan Adams
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Electron Density ◽  
Valence Electron ◽  
Coordination Shell ◽  
Bond Valence ◽  
Coordination Numbers ◽  
Valence Electron Density ◽  
Bond Valence Parameter

Based on a description of bond valence as a function of valence electron density, a systematic bond softness sensitive approach to determine bond-valence parameters and related quantities such as coordination numbers is elaborated and applied to determine bond-valence parameters for 706 cation–anion pairs. While the approach is closely related to the earliersoftBVparameter set, the newsoftNC1parameters proposed in this work may be simpler to apply in plausibility checks of crystal structures, as they follow the first coordination shell convention. The performance of thissoftNC1bond-valence parameter set is compared with that of the previously derivedsoftBVparameter set that also factors in contributions from higher coordination shells, and with a benchmarking parameter set that has been optimized following the conventional choice of a universal value of the bond-valence parameterb. The results show that a systematic adaptation of the bond-valence parameters to the bond softness leads to a significant improvement in the bond-valence parameters, particularly for bonds involving soft anions, and is safer than individual free refinements of bothR0andbfrom a limited number of reference cation environments.

scholarly journals Spotlight on Alkali Metals: The Structural Chemistry of Alkali Metal Thallides

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1013
Author(s):  
Stefanie Gärtner
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Alkali Metals ◽  
Valence Electron ◽  
Oxidation States ◽  
Valence Electron Concentration ◽  
Base Metals ◽  
Charge Balancing

Alkali metal thallides go back to the investigative works of Eduard Zintl about base metals in negative oxidation states. In 1932, he described the crystal structure of NaTl as the first representative for this class of compounds. Since then, a bunch of versatile crystal structures has been reported for thallium as electronegative element in intermetallic solid state compounds. For combinations of thallium with alkali metals as electropositive counterparts, a broad range of different unique structure types has been observed. Interestingly, various thallium substructures at the same or very similar valence electron concentration (VEC) are obtained. This in return emphasizes that the role of the alkali metals on structure formation goes far beyond ancillary filling atoms, which are present only due to charge balancing reasons. In this review, the alkali metals are in focus and the local surroundings of the latter are discussed in terms of their crystallographic sites in the corresponding crystal structures.

INTERFACE ELECTRON STRUCTURE OFTiC–NiAlCOMPOSITES

2012 ◽  
Vol 19 (05) ◽  
pp. 1250056
Author(s):  
X.-F. TIAN ◽  
W.-K. ZHANG ◽  
Y. QI
Keyword(s):  
Electron Density ◽  
Valence Electron ◽  
Electron Structure ◽  
Matrix Composites ◽  
Communication Interface ◽  
Valence Electron Structure ◽  
Valence Electron Density ◽  
Intermetallic Matrix ◽  
Intermetallic Matrix Composites ◽  
Set Up

Intermetallic matrix composites reinforced with ceramic particles such as TiC have received increasing attention in recent years due to the combined potential of ceramics and intermetallics to give a desirable balance of properties. But an understanding of some experimental results presented elsewhere has remained elusive. In this communication, interface valence electron structure of TiC–NiAl composites was set up on the basis of Pauling's nature of the chemical bond, and valence electron density ρ of different atomic states TiC and NiAl composites in various planes was determined. From the viewpoint of biphase interface electron density continuing, the corresponding experimental phenomena are explained.

Review of polyhedral distortions as a multi-scale minimization of the electric polarization and their correlations with physical properties

2006 ◽  
Vol 62 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Abderrahim Benabbas
Keyword(s):  
Physical Properties ◽  
Electron Density ◽  
Valence Electron ◽  
Cuprate Superconductors ◽  
Electric Polarization ◽  
Chemical Compositions ◽  
Multi Scale ◽  
Valence Electron Density ◽  
Formal Charge ◽  
Jahn Teller

The Jahn–Teller (JT) and non-Jahn–Teller polyhedral distortions are reviewed within the same context, based on a multi-scale minimization of the electric polarization by handling formal ionic valences and valence electron density. This model is applied to tetragonal distortions of octahedra, particularly in K2NiF4 structures with different formula types, along with doping. The predictions are always in good agreement with the observed data. In particular, the ferrodistortive order of JT distortions is obtained from formal charge polarizations, while the antiferrodistortive one is adopted when only the valence electron density is involved. The correlations between physical properties and octahedral elongations through the crystal structures on one side and chemical compositions on the other side are discussed according to this model for high-Tc cuprate superconductors and CMR manganites.

Investigation of chlorine valence electron density in SnCl4L2, SbCl5L and TiCl4L2 complexes

1995 ◽  
Vol 344 (1-2) ◽  
pp. 107-110 ◽  
Author(s):  
O.Kh. Poleshchuk ◽  
V.P. Elin ◽  
J. Koput ◽  
B. Nogaj ◽  
G.N. Dolenko
Keyword(s):  
Electron Density ◽  
Valence Electron ◽  
Valence Electron Density
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