Crystal structures bonds and reliance in MX (M = La, Ce...Yb and Sc, Ti...Zn; X = S, Se, Te)

1989 ◽  
Vol 54 (3) ◽  
pp. 551-565 ◽  
Author(s):  
Xavier Oudet
Keyword(s):  
Phase Transformation ◽  
Crystal Structures ◽  
Rare Earths ◽  
Valence Electron ◽  
Molecular Volume

Large variations of the molecular volume of the monochalcogenides of rare earths are attributed to cation-cation bond which involves one deep valence electron. Similar results are found with monochalgenides of 3d metals. The phase transformation Ceγ ⇄ Ceα is interpreted in a similar way bearing in mind the existence of compounds such as XeF4. This work introduces the notion of reliance which enlightens the notion of valence and is closely related, to the notion of intermediate and fluctuating valences.

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.

Effects of Transition Metals and Rare Earths on Iron-Carbon Micro Electrolysis Degrading Dyeing Effluent

2014 ◽  
Vol 1010-1012 ◽  
pp. 928-933
Author(s):  
Ju Chi Kuang ◽  
Xiao Gang Chen ◽  
Min Hua Chen
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Valence Electron ◽  
Zero Valent Iron ◽  
Effluent Treatment ◽  
Related Factors ◽  
Valence Electron Structure ◽  
Iron Catalysis ◽  
Orthogonal Experiments ◽  
Dyeing Effluent

The principle and methodology of effluent treatment by iron-carbon micro electrolysis were introduced in the paper. Then design of the orthogonal experiments for dyeing effluent treatment was formulated. Discussion of influences of related factors on effluent treatment followed. Results were got after the detailed analysis. Therefore, we deduced the mechanism that the cations of Transition Metal (TM) and rare earth (RE) assist of zero-valent irons catalyzing degradation of dyeing effluent. The mechanism is formed based on the following explanation. Cations of manganese and cobalt easily penetrate Fe0lattices, while Ce4+cations do it difficultly because of their larger radius. Thus Ce4+is weaker than both of Mn2+and Co2+for helping zero-valent irons to improve their activity. Furthermore, because the valence electron structure of Mn2+is more stable than that of Co2+, Mn2+is better for assisting zero-valent iron catalysis of degradation of dyeing effluent than Co2+. Therefore, ranking of influence for zero-valent iron catalysis activity from greatest to smallest is Mn2+, Co2+and Ce4+.

Zur Struktur und Dotierung von Selenosilikaten: die Kristallstruktur von Er2SeSiO4 und Er3,75Ca0,25Se2,75Cl0,25Si2O7 Structure and Doping of Seleno Silicates: the Crystal Structures of Er2SeSiO4 and Er3,75Ca0,25Se2,75Cl0,25Si2O7

1994 ◽  
Vol 49 (6) ◽  
pp. 733-740 ◽  
Author(s):  
Klaus Stöwe
Keyword(s):  
Crystal Structures ◽  
Structure Analysis ◽  
Rare Earths ◽  
Structure Determination ◽  
Lattice Parameters ◽  
Energy Dispersive ◽  
Space Group ◽  
X Ray ◽  
By Products

Well-shaped brown and pink isometric crystals were obtained as by-products of the synthesis of erbium selenides from the elements in evacuated and sealed silica ampoules with graphite inlets. They could be identified as erbium seleno mono- and disilicates by energy dispersive X-ray fluorescence and X-ray structure determination. The monosilicate Er2SeSiO4 crystallizes isotypically to Nd2SeSiO4 in the space group Pbcm with the lattice parameters a = 600.2(2), b = 688.0(2), c = 1075.2(2) pm and represents the second known seleno inosilicate of the rare earths. From X-ray structure analysis an isotypic relation between the disilicate Er3,75Ca0,25Se2,75Cl0,25Si2O7 and the compound Sm4S3Si2O7 was found, the former crystallizing in the space group I41/amd with the lattice parameters a - 1177.7(2) and c = 1376.5(2) pm. The doping o f the sorosilicate with the elements Ca and Cl originated from contam inations in the graphit inlets used in the procedure

Dimorphic ThNi2P2 with BaCu2S2 and CaBe2Ge2 Type Structure

1994 ◽  
Vol 49 (8) ◽  
pp. 1074-1080 ◽  
Author(s):  
Jörg H. Albering ◽  
Wolfgang Jeitschko
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Crystal Structures ◽  
Type Structure ◽  
Variable Parameters ◽  
Higher Symmetry ◽  
X Ray ◽  
Coordination Numbers ◽  
Structure Factors ◽  
High Temperature Form

Two modifications of ThNi2P2 were prepared in a tin flux at 850 °C (α-ThNi2P2) and 1000 °C (β-ThNi2P2). The crystal structures of both modifications were refined from single­crystal X-ray data. α-ThNi2P2 (BaCu2S2 type structure): Pnma. a = 819.69(5), b = 394.28(3), c = 981.54(7) pm. R = 0.028 for 32 variables and 654 structure factors: β-ThNi2P2 (CaBe2Ge2 type structure): P4/nmm, a = 408.5(1), c = 908.0(3) pm, R = 0.033 for 15 variable parameters and 261 F values. Although the two structures are closely related, they can be transformed into each other only by a reconstructive phase transformation. The differences and similari­ties of the two structures are discussed. The high temperature form has higher symmetry, a smaller number of variable positional parameters, and a tendency for higher coordination numbers.

Thermoelectric Properties of Ru2Si3-Based Chimney-Ladder Phases

2007 ◽  
Vol 561-565 ◽  
pp. 463-466 ◽  
Author(s):  
Kyosuke Kishida ◽  
Akira Ishida ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Crystal Structures ◽  
Thermoelectric Properties ◽  
Electron Concentration ◽  
Valence Electron ◽  
Valence Electron Concentration ◽  
Compositional Range ◽  
Wide Compositional Range ◽  
P Type ◽  
Semiconducting Behavior

The variations of the crystal structures and thermoelectric properties of the Ru1-xRexSiy chimney-ladder phases were studied as a function of the Re concentration. A series of chimney-ladder phases with a compositional formula of Ru1-xRexSi1.539+0.178x are formed in a wide compositional range, 0.14 ≤ x ≤ 0.76. The composition of the chimney-ladder phase is systematically deviated from the idealized composition satisfying the valence electron concentration rule: VEC=14. Measurements of thermoelectric properties reveal that the chimney-ladder phases exhibit n-type semiconducting behavior at low Re concentrations and p-type semiconducting behavior at high Re concentrations, which are well consistent with the prediction based on the deviation of the composition of the chimney-ladder phase from the idealized composition.

Four new zinc(ii) diphosphonates obtained via an ionothermal route: crystal structures and phase transformation behaviour

CrystEngComm ◽  
2017 ◽  
Vol 19 (18) ◽  
pp. 2500-2508 ◽  
Author(s):  
Li Zhang ◽  
Sanying Li ◽  
Lei Liu ◽  
Jinxiang Dong ◽  
Zhi Lin
Keyword(s):  
Phase Transformation ◽  
Crystal Structures ◽  
Transformation Behaviour

Crystal structures and phase transformation of two novel solvates of valnemulin hydrochloride

CrystEngComm ◽  
2018 ◽  
Vol 20 (5) ◽  
pp. 563-569 ◽  
Author(s):  
Jinbo Ouyang ◽  
Bing Na ◽  
Limin Zhou ◽  
Saijin Xiao ◽  
Guoxuan Xiong ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Crystal Structures ◽  
Valnemulin Hydrochloride

The crystal structures and phase transformation of two novel solvates of valnemulin hydrochloride have been studied.

Crystal structures and magnetic properties of rare earth tantalates RE3TaO7(RE = rare earths)

2004 ◽  
Vol 16 (23) ◽  
pp. 4103-4120 ◽  
Author(s):  
Makoto Wakeshima ◽  
Hiroaki Nishimine ◽  
Yukio Hinatsu
Keyword(s):  
Magnetic Properties ◽  
Rare Earth ◽  
Crystal Structures ◽  
Rare Earths
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