Atomanordnung und Strukturverfeinerung von Cancrinit

Jarchow, O.

doi:10.1524/zkri.1965.122.5-6.407

Cited by 95 publications

(38 citation statements)

References 3 publications

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“…These features seem to indicate the presence of a disordered distribution of H 2 O molecules. In fact, the IR spectrum of carbonate-dominant cancrinite (Ballirano et al 1995) shows two well-defined peaks located at 3607 and 3539 cm -1 , which correspond, according to the plot of Nakamoto et al (1955), to (Si,Al)O...OH 2 distances of 3.1 and 3.0 Å, in excellent agreement with the known refinements of the structure of this mineral (Jarchow 1965, Smolin et al 1981, Emiraliev & Yamzin 1982, Grundy & Hassan 1982.…”

Section: Methodssupporting

confidence: 72%

“…The structure refinements of carbonate-dominant cancrinite (Jarchow 1965, Smolin et al 1981, Emiraliev & Yamzin 1982, Grundy & Hassan 1982, Ge-substituted cancrinite (Belokoneva et al 1986), basic (i.e., hydroxyl-dominant) cancrinite (Bresciani Pahor et al 1982, Hassan & Grundy 1991, vishnevite (Hassan & Grundy 1984, Pushcharovskii et al 1989, pitiglianoite (Merlino et al 1991), bystrite (Pobedimskaya et al 1991a), and afghanite (Pobedimskaya et al 1991b) have shown that the H 2 O molecule of the "cancrinite" cage has one short distance (2.4 Å) and one long distance (2.9 Å) to the cations. Accordingly, we propose that the short W-A2 bond distance [2.53(7) Å] is coupled with the occupancy of the A3 site, leading to a long [3.15(4) Å] W-A3 bond distance.…”

Section: Cancrinite Cagesmentioning

confidence: 99%

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The Crystal Structure of Franzinite, the Ten-Layer Mineral of the Cancrinite Group

Ballirano¹,

Bonaccorsi²,

Maras³

et al. 2000

The Canadian Mineralogist

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Franzinite, ideally [(Na,K) 10 •2H 2 O, a feldspathoid belonging to the cancrinite group, has a tenlayer stacking sequence. Its structure was solved in the space group P321 to an R value of 5.96%. Cell parameters are a 12.916(1), c 26.543(3) Å. The framework, characterized by the stacking sequence ABCABACABC, contains regular alternations of two "cancrinite" and two "sodalite" cages along [0 0 z], and of two "sodalite" and one "losod" cages along [⅔ ⅓ z] and [⅓ ⅔ z]. The Si:Al ratio is equal to 1, and the framework has a perfectly ordered Si,Al distribution, as was found in liottite and afghanite, the 6-and 8-layer cancrinite-like minerals, respectively. The cages host a complex distribution of extra-framework cations (Ca, Na, K), (SO 4 ) 2-anions, and H 2 O molecules. The "losod" cage contains two sulfate groups aligned along z and separated by a triplet of cations. Two additional triplets of cations are located around the two sulfate groups. The two bases of the cage are occupied by calcium atoms, which make favorable bond-distances with the apical atoms of oxygen of the SO 4 tetrahedra within the cage. The two "cancrinite" cages share a common base and contain a segment of the ...Na-H 2 O…Na-H 2 O.... chain, which is a characteristic feature of the cancrinite, vishnevite, and pitiglianoite structures. The "sodalite" cages host one sulfate group that is always disordered and displaced from the three-fold axis. The (Ca, K, Na) cations are distributed among various split sites, each one with partial occupancy, showing marked similarity with the "sodalite" cages of the (SO 4 ) 2--and S 2--bearing minerals with sodalitetype structure.

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Section: Methodssupporting

confidence: 72%

Section: Cancrinite Cagesmentioning

confidence: 99%

The Crystal Structure of Franzinite, the Ten-Layer Mineral of the Cancrinite Group

Ballirano¹,

Bonaccorsi²,

Maras³

et al. 2000

The Canadian Mineralogist

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“…According to Jarchow (1965), the electron density distribution around O6 of the water molecule showed a strong possibility of disorder over the three positions around the 3 -fold axis. Grundy and Hassan (1982) also demonstrated another type of disorder at one of the oxygen atoms (O5) and at the carbon atom in two parts along the 6 3 -axis.…”

Section: X-ray Single-crystal Analysesmentioning

confidence: 99%

Asymmetric thermal vibrations of atoms and pyroelectricity in cancrinite

Isupova¹,

Ida²,

Kihara³

et al. 2010

Journal of Mineralogical and Petrological Sciences

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The crystal structure of CO 3 -cancrinite was analyzed by applying a generalized structure factor expression of the Gram -Charlier expansion to the least -squares refinement performed by using the X -ray intensities measured on single crystals at 173, 293, 473, and 673 K. No satellite reflection or diffuse scattering was observed. The space group is P6 3 with unit cell a = 1.2604(3) and c = 0.51144(8) nm at 173 K, and a = 1.2709(4) and c = 0.5202(6) nm at 823 K. The temperature behavior for the dehydration and the unit cell dimensions were considerably different from those previously reported for CO 3 -cancrinite, which shows superstructure reflections. Two position vectors were assigned to each of the framework atom sites or the CO 3 site for examining its asymmetric probability density function-one for the free energy minimum and another for the potential energy minimum. Two polarization vectors were obtained for a unit cell from those position vectors and ion charges. The rigid ion contributions to the pyroelectric coefficients p (σ) (measured under a constant stress σ) and the secondary coefficient p (2) were finally estimated from the temperature dependences of the polarization vectors.Keywords: Cancrinite, Asymmetric thermal vibrations, Pyroelectricity, Spontaneous polarization INTRODUCTIONCancrinite is a tectosilicate mineral belonging to a polar space group P6 3 (Grundy and Hassan, 1982), which allows the crystal to polarize electrically along the hexagonal c -axis. Figure 1 illustrates the structure of cancrinite in projections along [001] and [210]. Symmetrically independent atom sites obtained from the split -site refinement in the present study are shown in Figure 1a; the z -coordinates are rounded off and given in parentheses. Some measurements of the pyroelectric coefficients have been reported for CO 3 -cancrinite at temperatures 4.2 -500 K by Drozhdin et al. (1975) and Kozlov et al. (1989). These authors found that the temperature dependence of the pyroelectric coefficient p (σ) , which was measured under a constant mechanical stress σ, is non -monotonic, including sign changes below 100 K, and has some polarization relaxations. Most of these studies have pointed out the importance of water molecules in the absolute values of p (σ) , although the interpretation of temperature behaviors is not unique. Drozhdin et al. (1975) considered two cases, wherein the primary and secondary (the piezoelectric effect due to thermal expansions) effects are predominant, whereas Kozlov et al. (1989) considered the temperature dependence of the primary effect as the reason for the sign change. In a more general interpretation, another possibility has been pointed out on the basis of the compensation between the two values of the changes in polarization-one value for the aluminosilicate framework and another for one or more mobile structural elements possessing nonzero intrinsic dipole moments (Galitskii, 1981). Many compounds contain molecules or complexes in channels or voids in their structures, which ar...

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“…. [23,24]. Two structures have been found consisting of three layers, sodalite (SOD) with stacking sequence of ABC(A).…”

Section: Abc-6 Familymentioning

confidence: 99%

Stacking disorders in zeolites and open-frameworks – structure elucidation and analysis by electron crystallography and X-ray diffraction

Willhammar¹,

Zou²

2013

Zeitschrift für Kristallographie - Crystalline Materials

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Abstract. Intergrowth and stacking disorders are often found in minerals and synthetic zeolites and inorganic openframeworks. Structure elucidation of stacking disorders in these materials have been difficult and structure solution of stacking disorders in unknown zeolites and open-frameworks has been challenging. There exist no standard methods for structure analysis of such disordered materials. In this review we present various stacking disorders and intergrowth in a number of representative zeolite families containing stacking disorders. These include zeolite beta, SSZ-26/SSZ-33, ITQ-39, ABC-6, ZSM-48, SSZ-31, UTD-1, faujasite FAU/EMT, pentasil ZSM-5/ZSM-11, ITQ-13/ITQ-34, ITQ-22/ITQ-38 etc. Stacking disorders in open-frameworks containing mixed coordinations, including titanosilicates ETS-10 and ETS-4, and the silicogermanate SU-JU-14 are also described. Various crystallographic methods used for solving disordered structures are summarized. The methods include powder X-ray diffraction (PXRD), electron diffraction, high resolution transmission electron microscopy (HRTEM), and single-crystal X-ray diffraction. Examples of model building combined with simulations of PXRD and single crystal X-ray diffraction to verify the structure models are given.

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Atomanordnung und Strukturverfeinerung von Cancrinit

Cited by 95 publications

References 3 publications

The Crystal Structure of Franzinite, the Ten-Layer Mineral of the Cancrinite Group

The Crystal Structure of Franzinite, the Ten-Layer Mineral of the Cancrinite Group

Asymmetric thermal vibrations of atoms and pyroelectricity in cancrinite

Stacking disorders in zeolites and open-frameworks – structure elucidation and analysis by electron crystallography and X-ray diffraction

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