scholarly journals Zincalstibite-9R: the first nine-layer polytype with the layered double hydroxide structure-type

2012 ◽  
Vol 76 (5) ◽  
pp. 1337-1345 ◽  
Author(s):  
S. J. Mills ◽  
A. G. Christy ◽  
A. R. Kampf ◽  
R. M. Housley ◽  
G. Favreau ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Layered Double Hydroxide ◽  
Structure Type ◽  
Refractive Indices ◽  
Stacking Sequence ◽  
Oh Groups ◽  
Layer Stacking ◽  
Periodic Layer ◽  
Double Hydroxide ◽  
The Ideal

AbstractZincalstibite-9R, a new polytype in the hydrotalcite supergroup is reported from the Monte Avanza mine, Italy. It occurs as pale blue curved disc-like tablets flattened on {001} intergrown to form rosettes typically less than 50 μm in diameter, with cyanophyllite and linarite in cavities in baryte. Zincalstibite-9R is uniaxial (–), with refractive indices ω = 1.647(2) and ε = 1.626(2) measured in white light. The empirical formula (based on 12 OH groups) is (Zn1.092+Cu0.872+Al0.04)Σ2.00Al1.01(Sb0.975+Si0.02)Σ0.99(OH)12, and the ideal formula is (Zn,Cu)2Al(OH)6[Sb(OH)6]. Zincalstibite-9R crystallizes in space group R, with a = 5.340(2), c = 88.01(2) Å, V = 2173.70(15) Å3 and Z = 9. The crystal structure was refined to R1 = 0.0931 for 370 unique reflections [Fo > 4σ(F)] and R1 = 0.0944 for all 381 unique reflections. It has the longest periodic layer stacking sequence for a layered double hydroxide compound reported to date.

Crystal chemistry of natural layered double hydroxides: 4. Crystal structures and evolution of structural complexity of quintinite polytypes from the Kovdor alkaline-ultrabasic massif, Kola peninsula, Russia

2018 ◽  
Vol 82 (2) ◽  
pp. 329-346 ◽  
Author(s):  
Elena S. Zhitova ◽  
Sergey V. Krivovichev ◽  
Viktor N. Yakovenchuk ◽  
Gregory Yu. Ivanyuk ◽  
Yakov A. Pakhomovsky ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structural Information ◽  
Structural Complexity ◽  
Configurational Entropy ◽  
Direct Methods ◽  
Stacking Sequence ◽  
Layer Stacking ◽  
Complete Layer ◽  
Double Hydroxide ◽  
Double Hydroxides

AbstractTwo quintinite polytypes, 3R and 2T, which are new for the Kovdor alkaline-ultrabasic complex, have been structurally characterized. The crystal structure of quintinite-2T was solved by direct methods and refined to R1 = 0.048 on the basis of 330 unique reflections. The structure is trigonal, P$\bar 3$c1, a = 5.2720(6), c = 15.113(3) Å and V = 363.76(8) Å3. The crystal structure consists of [Mg2Al(OH)6]+ brucite-type layers with an ordered distribution of Mg2+ and Al3+ cations according to the $\sqrt 3 $ × $\sqrt 3 $ superstructure with the layers stacked according to a hexagonal type. The complete layer stacking sequence can be described as …=Ab1C = Cb1A=…. The crystal structure of quintinite-3R was solved by direct methods and refined to R1 = 0.022 on the basis of 140 unique reflections. It is trigonal, R$\bar 3$m, a = 3.063(1), c = 22.674(9) Å and V = 184.2(1) Å3. The crystal structure is based upon double hydroxide layers [M2+,3+(OH)2] with disordered distribution of Mg, Al and Fe and with the layers stacked according to a rhombohedral type. The stacking sequence of layers can be expressed as …=АB = BC = CA=… The study of morphologically different quintinite generations grown on one another detected the following natural sequence of polytype formation: 2H → 2T → 1M that can be attributed to a decrease of temperature during crystallization. According to the information-based approach to structural complexity, this sequence corresponds to the increasing structural information per atom (IG): 1.522 → 1.706 → 2.440 bits, respectively. As the IG value contributes negatively to the configurational entropy of crystalline solids, the evolution of polytypic modifications during crystallization corresponds to the decreasing configurational entropy. This is in agreement with the general principle that decreasing temperature corresponds to the appearance of more complex structures.

Crystal chemistry of natural layered double hydroxides. I. Quintinite-2H-3c from the Kovdor alkaline massif, Kola peninsula, Russia

2010 ◽  
Vol 74 (5) ◽  
pp. 821-832 ◽  
Author(s):  
S. V. Krivovichev ◽  
V. N. Yakovenchuk ◽  
E. S. Zhitova ◽  
A. A. Zolotarev ◽  
Y. A. Pakhomovsky ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Kola Peninsula ◽  
Direct Methods ◽  
Stacking Sequence ◽  
Layer Sequence ◽  
Layer Stacking ◽  
Double Hydroxide ◽  
Double Hydroxides ◽  
First Time ◽  
Alkaline Massif

AbstractThe crystal structure of quintinite-2H-3c, [Mg4Al2(OH)12](CO3)(H2O)3, from the Kovdor alkaline massif, Kola peninsula, Russia, was solved by direct methods and refined to an agreement index (R1) of 0.055 for 484 unique reflections with |Fo| ≥ 4σF. The mineral is rhombohedral, R32, a = 5.2745(7), c = 45.36(1) Å. The diffraction pattern of the crystal has strong and sharp Bragg reflections having h–k = 3n and l = 3n and lines of weak superstructure reflections extended parallel to c* and centred at h–k ≠ 3n. The structure contains six layers within the unit cell with the layer stacking sequence of …AC=CA=AC=CA=AC=CA… The Mg and Al atoms are ordered in metal hydroxide layers to form a honeycomb superstructure. The full superstructure is formed by the combination of two-layer stacking sequence and Mg-Al ordering. This is the first time that a long-range superstructure in carbonate-bearing layered double hydroxide (LDH) has been observed. Taking into account Mg-Al ordering, the unique layer sequence can be written as …=Ab1C=Cb1A=Ab2C=Cb2A=Ab3C=Cb3A=… The use of an additional suffix is proposed in order to distinguish between LDH polytypes having the same general stacking sequence but with different c parameters compared with the ‘standard’ polytype. According to this notation, the quintinite studied here can be described as quintinite-2H-3c or quintinite-2H-3c[6R], indicating the real symmetry.

From Structure Topology to Chemical Composition. XXIX. Revision of the Crystal Structure of Perraultite, NaBaMn4Ti2(Si2O7)2O2(OH)2F, a Seidozerite-Supergroup TS-Block Mineral from the Oktyabr'skii Massif, Ukraine, and Discreditation of Surkhobite

2021 ◽  
Author(s):  
Elena Sokolova ◽  
Maxwell C. Day ◽  
Frank C. Hawthorne ◽  
Atali A. Agakhanov ◽  
Fernando Cámara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Structure Type ◽  
Titanium Silicate ◽  
Space Group ◽  
Structure Topology ◽  
Ideal Composition ◽  
Using Data ◽  
Cation Sites ◽  
The Ideal

ABSTRACT The crystal structure of perraultite from the Oktyabr'skii massif, Donetsk region, Ukraine (bafertisite group, seidozerite supergroup), ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4, was refined in space group C to R1 = 2.08% on the basis of 4839 unique reflections [Fo > 4σFo]; a = 10.741(6), b = 13.841(8), c = 11.079(6) Å, α = 108.174(6), β = 99.186(6), γ = 89.99(1)°, V = 1542.7(2.7) Å3. Refinement was done using data from a crystal with three twin domains which was part of a grain used for electron probe microanalysis. In the perraultite structure [structure type B1(BG), B – basic, BG – bafertisite group], there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H – heteropolyhedral, O – octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Mn4 apfu. There is no order of Mn and Fe2+ in the O sheet. The MH octahedra and Si2O7 groups constitute the H sheet. The ideal composition of the two [6]MH sites is Ti2 apfu. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. The AP(1) site is occupied by Ba and the AP(2) site by K > Ba; the ideal composition of the AP(1,2) sites is Ba apfu. The BP(1) and BP(2) sites are each occupied by Na > Ca; the ideal composition of the BP(1,2) sites is Na apfu. We compare perraultite and surkhobite based on the work of Sokolova et al. (2020) on the holotype sample of surkhobite: space group C , R1 = 2.85 %, a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; new EPMA data. We show that (1) perraultite and surkhobite have identical chemical composition and ideal formula NaBaMn4Ti2(Si2O7)2O2(OH)2F; (2) perraultite and surkhobite are isostructural, with no order of Na and Ca at the BP(1,2) sites. Perraultite was described in 1991 and has precedence over surkhobite, which was redefined as “a Ca-ordered analogue of perraultite” in 2008. Surkhobite is not a valid mineral species and its discreditation was approved by CNMNC IMA (IMA 20-A).

Farneseite, a new mineral of the cancrinite - sodalite group with a 14-layer stacking sequence: occurrence and crystal structure

2006 ◽  
Vol 17 (6) ◽  
pp. 839-846 ◽  
Author(s):  
Fernando Cá mara ◽  
Fabio Bellatreccia ◽  
Giancarlo Della Ventura ◽  
Annibale Mottana
Keyword(s):  
Crystal Structure ◽  
New Mineral ◽  
Stacking Sequence ◽  
Layer Stacking

scholarly journals Morphological and Thermal Properties of Poly(Vinyl Alcohol)/Layered Double Hydroxide Hybrid Nanocomposite Fibers

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
A. F. Al Naim ◽  
J. Mazher ◽  
S. S. Ibrahim
Keyword(s):  
Crystal Structure ◽  
Heat Treatment ◽  
Layered Double Hydroxide ◽  
Vinyl Alcohol ◽  
Separation Distance ◽  
Molecular Vibration ◽  
Poly Vinyl Alcohol ◽  
Rapid Weight Loss ◽  
Different Temperatures ◽  
Double Hydroxide

Nanolayered particulate of Zn-based layered double hydroxide (LDH) was prepared by a low temperature greener sol-gel method. X-ray diffraction (XRD) studies were performed on the particles annealed at different temperatures. Hexagonal crystal structure of the as-grown LDH particulates was observed. The crystal structure was modified to tetragonal structure of layered double oxide (LDO) on annealing at 250°C. Rietveld fittings showed a collapse of interlayer separation distance along the preferred orientation of the LDH particles as a result of heat treatment. Further, LDH particles were used as fillers of electrospun poly(vinyl alcohol) (PVA) fibers. Heat treatment of the polymer fibers was also performed at different temperatures, and thermal changes were studied by thermogravimetric analysis (TGA), Raman spectroscopy, and scanning electron microscopy (SEM) techniques. Improved interaction of fibers with LDH nanoparticles was observed and ascribed to LDH-related LDO phase transformation at higher temperature. Thermal mechanisms of the rapid weight loss in filled fibers were discussed in comparison to the pure PVA fiber losses. Experimental Raman frequencies of the composite fibers were compared with the calculated Raman modes of the enol and ZnO monomers. The molecular vibration frequencies were found to differ significantly due to heat treatment. Finally, the role filler in the faster and greener thermal decomposition of polymeric fibers was also discussed in the present work.

Crystal structure of nickel manganese-layered double hydroxide@cobaltosic oxides on nickel foam towards high-performance supercapacitors

CrystEngComm ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 470-477 ◽  
Author(s):  
Huihua Peng ◽  
Chuan Jing ◽  
Jie Chen ◽  
Deyi Jiang ◽  
Xiaoying Liu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Layered Double Hydroxide ◽  
High Performance ◽  
Rational Design ◽  
Electrode Materials ◽  
Nickel Foam ◽  
Double Hydroxide ◽  
Nickel Manganese

Rational design of the crystal structures of electrode materials is considered as an important strategy to construct high-performance supercapacitors.

Cannonite [Bi2O(SO4)(OH)2] from Alfenza (Crodo, Italy): crystal structure and morphology

2013 ◽  
Vol 77 (8) ◽  
pp. 3067-3079 ◽  
Author(s):  
G. C. Capitani ◽  
T. Catelani ◽  
P. Gentile ◽  
A. Lucotti ◽  
M. Zema
Keyword(s):  
Crystal Structure ◽  
Cleavage Plane ◽  
Structure Refinement ◽  
Molecular Water ◽  
Hydrogen Atoms ◽  
Oh Groups ◽  
Cell Parameters ◽  
Difference Fourier ◽  
Raman And Ir Spectroscopy ◽  
The Ideal

AbstractCanonite from Alfenza grows as crowded, radiating, acicular aggregates covering bismuthinite crystals. Individual crystals have a lozenge-shaped habit on {010}, the presumed cleavage plane of cannonite. Crystal structure refinements in the P21/c space group of two single crystals led to the following cell parameters: a = 7.7196(5) Å, b = 13.8856(9), c = 5.6980(4), b = 109.174(1)º (R1 = 0.0424); and a = 7.7100(8), b = 13.8717(14), c = 5.6939(6), b = 109.155(2)º (R1 = 0.0438). Hydrogen atoms were also localized in the density-difference Fourier map and refined with soft restraints on the bond distances. Raman and IR spectroscopy confirm the presence of OH groups and the absence of molecular water, and deliver OH···O geometry wholly comparable with the structure refinement. Electron microprobe analyses revealed no significant levels of elements other than those expected in the ideal formula except fluorine which was present up to 0.14 a.p.f.u. The crystal structure can be described in terms of anion-centred OBi4 edge-sharing tetrahedra forming chains running parallel to z and strongly cemented along x by isolated SO4 tetrahedra. Each OBi4 tetrahedron is further connected along y by OH groups, making walls of composition Bi4O2(SO4)2(OH)4 parallel to (010). These walls are tied to each other along y by fewer Bi–O–S bridges and weaker OH···O bonds.

Defect Crystal Structure of Low Temperature Modifications of Li2MO3 (M=Ti, Sn) and Related Hydroxides

2010 ◽  
Vol 63 ◽  
pp. 352-357 ◽  
Author(s):  
Nadezda V. Tarakina ◽  
Tatiana A. Denisova ◽  
Yana V. Baklanova ◽  
Lidia G. Maksimova ◽  
Vladimir G. Zubkov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Type ◽  
High Concentration ◽  
X Ray ◽  
Space Groups ◽  
Defect Crystal ◽  
Double Hydroxide ◽  
Metal Layers ◽  
Neutral Metal

Crystal structures of Li2MO3 (M=Sn, Ti) and TiO(OH)2 have been studied in detail and refined using X-ray powder diffraction data. All compounds posses a high concentration of defects in the structure. The crystal structures of the Li2MO3 salts obtained at 700°C reveal stacking faults of LiM2 metal layers, which leads to the appearance of short-range order in three possible space groups: C2/c, C2/m, P3112. The possibility to stabilize this imperfect state increases the mobility of the Li+ ions in the Li2TiO3 structure and allows the complete exchange of lithium by hydrogen in acid water solutions with formation of TiO(OH)2. The crystal structure of TiO(OH)2 belongs to the layered double hydroxide structure type with the 3R1 sequence of oxygen layers and can be described as a stacking of charge-neutral metal oxyhydroxide slabs [(OH)2OTi2O(OH)2].

Crystal structure of a new representative of the cancrinite group with a 12-layer stacking sequence of tetrahedral rings

2004 ◽  
Vol 49 (4) ◽  
pp. 635-642 ◽  
Author(s):  
K. A. Rozenberg ◽  
A. N. Sapozhnikov ◽  
R. K. Rastsvetaeva ◽  
N. B. Bolotina ◽  
A. A. Kashaev
Keyword(s):  
Crystal Structure ◽  
Stacking Sequence ◽  
Layer Stacking

scholarly journals Polytypism, polymorphism, and superconductivity in TaSe2−xTex

2015 ◽  
Vol 112 (11) ◽  
pp. E1174-E1180 ◽  
Author(s):  
Huixia Luo ◽  
Weiwei Xie ◽  
Jing Tao ◽  
Hiroyuki Inoue ◽  
András Gyenis ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Physical Properties ◽  
Single Layer ◽  
Large Family ◽  
Layered Materials ◽  
Stacking Sequence ◽  
Superconducting Transition ◽  
Surprising Effect ◽  
Layer Stacking ◽  
Structural Layer

Polymorphism in materials often leads to significantly different physical properties—the rutile and anatase polymorphs of TiO2 are a prime example. Polytypism is a special type of polymorphism, occurring in layered materials when the geometry of a repeating structural layer is maintained but the layer-stacking sequence of the overall crystal structure can be varied; SiC is an example of a material with many polytypes. Although polymorphs can have radically different physical properties, it is much rarer for polytypism to impact physical properties in a dramatic fashion. Here we study the effects of polytypism and polymorphism on the superconductivity of TaSe2, one of the archetypal members of the large family of layered dichalcogenides. We show that it is possible to access two stable polytypes and two stable polymorphs in the TaSe2−xTex solid solution and find that the 3R polytype shows a superconducting transition temperature that is between 6 and 17 times higher than that of the much more commonly found 2H polytype. The reason for this dramatic change is not apparent, but we propose that it arises either from a remarkable dependence of Tc on subtle differences in the characteristics of the single layers present or from a surprising effect of the layer-stacking sequence on electronic properties that are typically expected to be dominated by the properties of a single layer in materials of this kind.

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