Tris(ethylenediamine)nickel(II) sulphate at 110 K. Structure determination in the presence of twinning

Jameson, G. B.; Schneider, R.; Dubler, E.; Oswald, H. R.

doi:10.1107/s0567740882010711

Cited by 29 publications

(22 citation statements)

References 10 publications

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confidence: 99%

“…Twinning by merohedry and corresponding procedures for the X-ray crystal structure determination play an important role, as was pointed out by Catti & Ferraris (1976). A comprehensive article on crystal structure determination in the presence of twinning was presented by Jameson, Schneider, Dubler & Oswald (1982).We have defined twin II to be represented by the stronger set of reflections of the unit cell a, b, c, fl in the space group P2~. The ab plane acts as a mirror, generating twin I and necessitating the collection of intensity data with the larger cell a, b, 2c, /3.…”

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The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Schmalle¹,

Williams²,

Reller³

et al. 1993

Acta Crystallogr B Struct Sci

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LaaTi207, Mr = 485.613, monoclinic, P2~, a = 7.812(2), b= 5.5440 (7), c= 13.010 (2) A, /3 = 98.66 (1) °, V = 557.0 (4)/~3, Z = 4, T = 298 K, Dx = 5.790 Mg m -3, A(Mo Ka) = 0.71073 A, /z = 17.86 mm-1, F(000) = 856. The crystals are twinned. The twin I and twin II intensities are superimposed in reciprocal-lattice layers with h even. The a* and b* axes of the twin components run antiparallel. The angle between atwin* i and atwin* n is 17.12 °. The twinning operation has been identified to be a mirror plane perpendicular to the c* direction affecting only the oxygen positions in the structure: La and Ti atoms lie on an orthorhombic sublattice unchanged by the twinning. The structure refined on [FI 2 to R = 0.040, wR = 0.085 for 7972 observed reflections with I> 3tr(l). The refinement was carried out by * Author to whom all correspondence should be addressed. Present address: JASCO International Co. Ltd., 4-21 Sennin-cho 2-chome, Hachioji City, Tokyo 193, Japan.0108-7681/93/020235-10506.00 inclusion of the contributions from the two twin elements simultaneously, with the use of appropriate matrices to relate the atomic coordinates and reflection indices of each of the twin elements. The twin volume fraction was also refined and gave a = 0.1108 (3) as the volume fraction of twin I. The enantiomorphs in twin I and twin II have been shown to be opposite by refinement, on IF[, of the enantiopole, or Flack's x, parameter against reflection data that had been separated into separate sets for each twin element. Subsequently, several refinements, on IF1, of the twinned data set with the use of all possible combinations of enantiomorphs of each twin element yielded the best R/wR values (0.040 and 0.056) when the twin components contained opposite enantiomorphs. The general features of the structure determined by Gasperin [Acta Cryst. (1975), B31, 2129-2130] could be confirmed: the twins comprise distorted (4 + 1 + 1) TiO6 octahedra sharing vertices to form infinite perovskite-like layers three octahedra thick, bound by crystallographic © 1993 International Union of Crystallography 236 TWIN STRUCTURE OF La2Ti207 shears in the a direction. La atoms occupy distorted perovskitic A sites and interlayer sites. La2Ti207 is a member of an homologous series of An ÷ ,Bn ÷ 103n ÷ 5 (0 -< n --_ oo) compounds with n = 3. IntroductionLa2Ti207 belongs to a relatively small family of layered perovskite-related materials (Brandon & Megaw, 1970;Gasperin, 1975;Ishizawa, Marumo, Kawamura & Kimura, 1975). There are also a number of A2B207 alkali-metal niobates and tantalates adopting this structure type [for example, Ca2Nb207 (Brandon & Megaw, 1970) and Sr2Nb207 (Ishizawa et al., 1975)]; the optical and piezo-and ferroelectric properties of many of these phases are of interest (Nanamatsu, Kimura, Doi & Takahashi, 1971;Nanamatsu, Kimura & Kawamura, 1975). Gasperin, from her structure determination, indicated that La2Ti207 is a member of an homologous series of layered structures built from {110} perovskitic slabs differing in thick...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Schmalle¹,

Williams²,

Reller³

et al. 1993

Acta Crystallogr B Struct Sci

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“…Crystal mosaicities as determined by oJ-scans with a tube take-off angle of 2.4 ° were ~0.14 ° -values typical in this laboratory for reasonable quality crystals. Orientation and cell parameters: determined using 17 automatically centered reflections in the range 40.16 ° <20<41.81 ° with MoK~ 1 radiation (2= 0.70926 A); data measured: ~5000 reflections +hkl, to 20-60°; scan range: 0.9 ° below K~t~ to 0.9 ° above Ka2, slight peak truncation on high-20 side (<3%) chosen to avoid problems with overlapping reflections; scan speed: 2.0 ° min -1 in 20 with weak reflections rescanned cumulatively up to three times or until criterion 1 > 5a I satisfied (Lenhert, 1975); data processing: University of Zfirich crystallographic program library (Jameson, Schneider, Dubler & Oswald, 1982); Lorentz, polarization and absorption corrections; crystal: flattened needle 0.33 x 0.15 x 0.10mm, 2-29 x 10-3mm 3, transmission factors 0.160-0.360; neutral-atom scattering factors and anomalousdispersion corrections from International Tables for X-ray Crystallography (1974). To provide the necessary data so that the accuracy of this structure can be assessed a detailed description is supplied.…”

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Orthorhombic barium orthotitanate, α'-Ba2TiO4

Günter¹,

Jameson²

1984

Acta Crystallogr C

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“…NO 3 À in NaNO 3 or SO 2À 4 in [Nien 3 ]SO 4 (en = ethylenediamine), as found by Jameson et al (1982). In this last rotational type reconstructive transitions can also arise, as with ligand rotation in ferrocene (Seiler & Dunitz, 1982).…”

Section: Introductionmentioning

confidence: 61%

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI₂(dmf)₂

Edwards¹,

Easteal²,

Gladkikh³

et al. 1998

Acta Crystallogr Sect B

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At 228 K crystals of ZnI 2 (dmf) 2 show a reversible phase transition which does not disrupt the lattice. Above the transition temperature the space group is C2/c and the cell contains eight symmetrically equivalent molecules. Cooling to below the transition temperature has little effect on the cell parameters or on the Zn-and I-atom positions, but the space group is now P2 1 /n and the asymmetric unit comprises two conformationally different molecules. These arise from cooperative rotations of either ca +25 or À43 about the ZnÐO bond of one of the dmf ligands in the high-temperature form. This displacive transition involves large movements of some atoms. The corresponding chloride and bromide are isomorphous with the higher temperature C2/c form, but it is only with the iodide that the weaker intermolecular forces permit the unusual phase change. The transition has been followed by differential scanning calorimetry, which gives an enthalpy change of 1.44 (5) kJ mol À1.

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Tris(ethylenediamine)nickel(II) sulphate at 110 K. Structure determination in the presence of twinning

Cited by 29 publications

References 10 publications

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Orthorhombic barium orthotitanate, α'-Ba2TiO4

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI₂(dmf)₂

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Tris(ethylenediamine)nickel(II) sulphate at 110 K. Structure determination in the presence of twinning

Cited by 29 publications

References 10 publications

The twin structure of La2Ti2O7: X-ray and transmission electron microscopy studies

The twin structure of La2Ti2O7: X-ray and transmission electron microscopy studies

Orthorhombic barium orthotitanate, α'-Ba2TiO4

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI2(dmf)2

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The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI₂(dmf)₂