Search results for: Natalia M. Laptash

Items from 1 to 9 out of 9 results

article

Fluxional seven‐coordinated fluorido‐ and oxofluoridotantalates

Anatoly A. Udovenko, Arseny B. Slobodyuk, Tatiana B. Emelina, Natalia M. Laptash

Acta Crystallographica Section B > 75 > 6 > 1115 - 1125

Seven‐coordinated (NH₄)₂TaF₇, Rb₂TaF₇ and Rb₃TaOF₆ were synthesized in single‐crystal form and their structures were determined. A monocapped trigonal prism (CTP) or a pentagonal bipyramid (PB) of the TaF₇²⁻ anion are stereochemically nonrigid and coexist in the first two compounds as a result of strong intraspheric dynamics. Upon cooling, tetragonal Rb₂TaF₇ undergoes a first‐order phase transition...

article

Ammonium tantalum oxide fluorides: new features of dynamic disorder

Anatoly A. Udovenko, Natalia M. Laptash

Acta Crystallographica Section B > 75 > 6 > 1164 - 1173

Ammonium fluoride salts of seven‐ and eight‐coordinated tantalum were grown in the form of well shaped single crystals at different pH of solutions, and their crystal structures were determined by X‐ray diffraction. The first one, (NH₄)₃TaOF₆, belongs to elpasolite‐type structure (, Z = 4) and is characterized by strong dynamic disorder. The ligand atoms (O and F) are each distributed in three positions...

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Orientational disorder and phase transitions in ammonium oxofluorovanadates, (NH₄)₃VOF₅ and (NH₄)₃VO₂F₄

Anatoly A. Udovenko, Evgeny I. Pogoreltsev, Yuri V. Marchenko, Natalia M. Laptash

Acta Crystallographica Section B > 73 > 6 > 1085 - 1094

Single crystals of (NH₄)₃VOF₅ and (NH₄)₃VO₂F₄ were obtained from aqueous fluoride solutions and phase transitions in these compounds were investigated using X‐ray diffraction, differential scanning microcalorimetry (DSM) and vibrational spectroscopy. The room‐temperature (RT) phases of these compounds belong to orthorhombic symmetry [Immm and I222, Z = 6, for (NH₄)₃VOF₅ and (NH₄)₃VO₂F₄, respectively]...

article

Anomalous behaviour of thermodynamic properties at successive phase transitions in (NH4)3GeF7

Evgeniy V. Bogdanov, Andrey V. Kartashev, Evgeniy I. Pogoreltsev, Mikhail V. Gorev, more

Journal of Solid State Chemistry > 2017 > 256 > C > 162-167

Heat capacity, thermal dilatation, susceptibility to hydrostatic pressure and dielectric properties associated with succession of three phase transitions below room temperature in double fluoride salt (NH₄)₃GeF₇ were studied. A possible transformation into the parent Pm-3m cubic phase was not observed up to the decomposition of compound. Nonferroelectric nature of structural distortions was confirmed...

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Crystallographic features of ammonium fluoroelpasolites: dynamic orientational disorder in crystals of (NH₄)₃HfF₇ and (NH₄)₃Ti(O₂)F₅

Anatoly A. Udovenko, Alexander A. Karabtsov, Natalia M. Laptash

Acta Crystallographica Section B > 73 > 1 > 1 - 9

A classical elpasolite‐type structure is considered with respect to dynamically disordered ammonium fluoro‐(oxofluoro‐)metallates. Single‐crystal X‐ray diffraction data from high quality (NH₄)₃HfF₇ and (NH₄)₃Ti(O₂)F₅ samples enabled the refinement of the ligand and cationic positions in the cubic (Z = 4) structure. Electron‐density atomic profiles show that the ligand atoms are distributed in a mixed...

article

Thermal, structural, optical, dielectric and barocaloric properties at ferroelastic phase transition in trigonal (NH4)2SnF6: A new look at the old compound

Igor N. Flerov, Andrey V. Kartashev, Mikhail V. Gorev, Evgeniy V. Bogdanov, more

Journal of Fluorine Chemistry > 2016 > 183 > C > 1-9

Structural phase transition P-3m1↔P-1 of the first order and nonferroelectric nature was found in (NH₄)₂SnF₆ at about 110K in the process of thermal, optical, dielectric and X-ray studies.Order-disorder transformation is accompanied by large changes of entropy (ΔS₀=16.4J/molK) and volume (ΔV₀/V≈1%). The structural model associated with three orientations of NH₄ tetrahedra in P-3m1 phase and their...

article

Dinuclear oxofluorometallates as a new structural type of d⁰ transition metal oxofluoride compound

Anatoly A. Udovenko, Natalia M. Laptash

Acta Crystallographica Section B > 68 > 6 > 602 - 609

Five isomorphous d⁰ transition metal oxofluoride compounds A₃[M₂O_xF_11 − x]·(AF)_0.333 (A = K, Rb, NH₄; M = Nb, Mo, W; x = 2, 4) have been synthesized from acid fluoride solutions, and their crystal structures have been determined by single‐crystal X‐ray diffraction. The basic structural building units are dinuclear M₂X₁₁ (dimers) formed from NbOF₅ or Mo(W)O₂F₄ octahedra connected by the fluorine bridging...

article

Dynamic orientational disorder in crystals of fluoroelpasolites, structural refinement of (NH₄)₃AlF₆, (NH₄)₃TiOF₅ and Rb₂KTiOF₅

Anatoly A. Udovenko, Natalia M. Laptash

Acta Crystallographica Section B > 67 > 6 > 447 - 454

Room‐temperature crystal structures of triammonium hexafluoroaluminate, (NH₄)₃AlF₆ (I), and triammonium oxopentafluorotitanate, (NH₄)₃TiOF₅ (II), were refined, and the crystal structures of dirubidium potassium oxopentaflourotitanate, Rb₂KTiOF₅, at 297 K (III) and 218 K (IV) were determined using single‐crystal X‐ray diffraction techniques. In ammonium fluoroelpasolites [(I) and (II)], the ligand...

article

Orientational disorder and phase transitions in crystals of dioxofluoromolybdate, (NH₄)₂MoO₂F₄

Anatoly A. Udovenko, Alexander D. Vasiliev, Natalia M. Laptash

Acta Crystallographica Section B > 66 > 1 > 34 - 39

Dioxotetrafluoromolybdate, (NH₄)₂MoO₂F₄, was synthesized in a single‐crystal form and its structures [(I) at 297 K and (II) at 223 K] were determined by X‐ray diffraction. Two independent states of a cis‐MoO₂F₄ octahedron are characteristic of static and dynamic disorder in structure (I). The dynamically disordered Mo atom is displaced from the symmetry axis producing four possible orientations of...

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Keywords

CRYSTAL STRUCTURE (3)
DYNAMIC ORIENTATIONAL DISORDER (3)
FLUORIDES (3)
PHASE TRANSITIONS (3)
VIBRATIONAL SPECTRA (3)
ELECTRON‐DENSITY PROFILES (2)
ENTROPY (2)
PHASE TRANSITION (2)
SEVEN‐COORDINATION (2)
AMMONIUM (1)
AMMONIUM OXOFLUOROMOLYBDATE (1)
AMMONIUM OXOFLUOROVANADATES (1)
BAROCALORIC EFFECT (1)
BRIDGING FLUORINE ATOMS (1)
CRYSTAL STRUCTURES (1)
DIFFERENTIAL SCANNING MICROCALORIMETRY (1)
DINUCLEAR OXOFLUOROMETALLATES (1)
DYNAMIC AND STATIC ORIENTATIONAL DISORDER (1)
DYNAMIC DISORDER (1)
EIGHT‐COORDINATION (1)
ELECTRON DENSITY PROFILE (1)
FLUOROELPASOLITES (1)
FLUORO‐ AND OXOFLUOROELPASOLITES (1)
FLUXIONALITY (1)
HEAT CAPACITY (1)
HIGH PRESSURE (1)
MEROHEDRAL TWINS (1)
NMR (1)
ORIENTATIONAL DISORDER (1)
OXIDE FLUORIDES (1)
STRUCTURAL DISORDER (1)
SYNCHRONOUS TI—O AND TI—F STRETCHING VIBRATION (1)
TANTALUM (1)
TANTALUM FLUORIDES (1)
THERMAL EXPANSION (1)
VIBRATIONAL SPECTROSCOPY (1)
X‐RAY DIFFRACTION (1)
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Wiley (7)
Elsevier (2)

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Search results for: Natalia M. Laptash

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