The crystal structure of iron(II) diphosphate, Fe2P2O7

Stefanidis, T.; Nord, Anders G.

doi:10.1524/zkri.1982.159.14.255

Cited by 22 publications

(11 citation statements)

References 7 publications

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“…There are several structure-types in which the A 2 B 2 O 7 compounds crystallize. The structure of ␥-Cu 2 V 2 O 7 is most closely related to the structure of triclinic ␤-Fe 2 P 2 O 7 (Stefanidis & Nord 1982, Hoggins et al 1983. The unit-cell dimensions of ␤-Fe 2 P 2 O 7 (a 5.517, b 5.255, c 4.488 Å, ␣ 98.73, ␤ 98.33, ␥ 103.81°) are related to those of ␥-Cu 2 V 2 O 7 ( Table 1), except that the c parameter of ␥-Cu 2 V 2 O 7 is doubled owing to the higher degree of distortion of the V 2 O 7 groups in comparison to the P 2 O 7 groups.…”

Section: Relationships To the A 2 B 2 X 7 Compoundsmentioning

confidence: 96%

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

Krivovichev¹,

Филатов²,

Cherepansky³

et al. 2005

The Canadian Mineralogist

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Single crystals of ␥-Cu 2 V 2 O 7 were obtained by the method of chemical transport reactions. The crystal structure [triclinic, P1, a 5.0873(10), b 5.8233(11), c 9.4020(18) Å, ␣ 99.780(3), ␤ 97.253(3), ␥ 97.202(3)°, V 269.20(9) Å 3 , Z = 2] has been solved by direct methods and refined to R 1 = 0.021 (wR 2 = 0.049) using 949 unique observed reflections with |F o | ≥ 4 F . The atomic arrangement contains two symmetrically independent Cu 2+ cations. The Cu(1) site is coordinated by six O atoms to form a distorted Cu(1)O 6 octahedron, whereas the Cu (2) site is coordinated by five O atoms arranged at the vertices of an elongate Cu(2)O 5 square pyramid. Two symmetrically independent V 5+ cations are tetrahedrally coordinated by four O atoms each. The O(5) atom bridges the V(1)O 4 and V(2)O 4 tetrahedra. The Cu(1)O 6 octahedra and Cu(2)O 5 square pyramids form two types of chains running parallel to the a axis. The chains are linked by V 2 O 7 groups into a complex heteropolyhedral framework. The structure of ␥-Cu 2 V 2 O 7 is closely related to the structures of ␣-Cu 2 V 2 O 7 (blossite) and ␤-Cu 2 V 2 O 7 (ziesite). The three structures are based upon chains of edge-sharing Cu 2+ polyhedra linked by V 2 O 7 groups. Similarity of the structure of ␥-Cu 2 V 2 O 7 to the structures of blossite and ziesite indicates possible formation of this phase under natural conditions, such as those that occur in "dry" high-temperature fumaroles of the Izalco (El Salvador) and Tolbachik (Kamchatka, Russia) volcanoes. The structure of ␥-Cu 2 V 2 O 7 can also be considered as a triclinically distorted derivative of the ␤-A 2 P 2 O 7 structure-type.

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Section: Relationships To the A 2 B 2 X 7 Compoundsmentioning

confidence: 96%

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

Krivovichev¹,

Филатов²,

Cherepansky³

et al. 2005

The Canadian Mineralogist

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“…The crystal structure of Fe2P207 was determined by Stefanidis & Nord (1982) in space group P1, with Z=I.…”

Section: (Q) Diiron(ii) Diphosphate Fe2p207mentioning

confidence: 99%

“…More likely is that Stefandis & Nord have omitted the weak reflections Marsh (1981) has shown that such deletion of weak reflections biases the statistical tests towards acentric distributions. Hoggins et al (1983) in their paper took note of the work of Stefanidis & Nord (1982) and argued for a centrosymmetric structure on the basis of their statistical tests, and because of the high correlations between related parameters and the nonpositivedefinite temperature factors encountered when they refined the structure in the noncentrosymmetric space group.…”

Section: (Q) Diiron(ii) Diphosphate Fe2p207mentioning

confidence: 99%

“…However, they are real and should not be neglected in the course of a crystal structure determination. (Stefanidis & Nord, 1982) and in space group Pi ( Hoggins et al, 1983), compared with the calculated values according to the method of Baur (1970,1974); O atoms O(1) and O(7), 0(2) and O(6), as well as 0(3) Recently the crystal structure of Ca2KH7(PO4)a.-2H20 was determined both by X-ray and by neutron diffraction (Prince, Takagi, Mathew & Brown, 1984). The X-ray refinement is reported in space group P1.…”

Section: (Q) Diiron(ii) Diphosphate Fe2p207mentioning

confidence: 99%

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How to avoid unnecessarily low symmetry in crystal structure determinations

Baur¹,

Тиллманнс²

1986

Acta Crystallogr Sect B

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A check of recent volumes of Acta Crystallographica and Crystal Structure Communications shows that about 3% of all recently published crystal structures were described with too low symmetry. Three categories of error are recognized: (1) both Laue class and crystal system are wrong; (2) only the Laue class is wrong; (3) Laue class and crystal system are correct, but an inversion center is missing. Category (1) cases can be most easily diagnosed by calculating the reduced cell and its Niggli matrix. Category (3) cases are most easily recognized during full-matrix leastsquares refinement from singularities, high correlations between parameters and poor convergence. The omission of an inversion center will not result in a singular matrix when all atoms in the centrosymmetric cell are in special positions which become general positions in the noncentrosymmetric cell. Once the refinement is completed structures with a missing inversion center can be recognized by unusually high e.s.d.'s, especially for the highly correlated parameters, and by large distortions of observed bond * Present address: Mineralogisches Institut, Universitiit Wiirzburg, Am Hubland, D-8700 Wiirzburg, Federal Republic of Germany. distances and angles from accepted values. Such distortions often show up as splitting of the centrosymmetrically related atomic positions into positions whose average is close to the true centrosymmetric positions. A mechanical application of the R-ratio test should be avoided; it can easily lead to wrong conclusions. Proof of higher symmetry must be obtained from the diffraction data. The presence of more than one effective formula per asymmetric unit should always be reason to check for higher symmetry. Cases in all three categories can be checked for the occurrence of higher symmetry by searching for regularities in bond lengths and angles or in the positional coordinates of the atoms. The most systematic way for such searches is the simple, but powerful method of topological analysis of crystal structures. For six structures which previously had been described with too low symmetry higher-symmetry descriptions are provided.

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“…Impurities of ferric iron or Fe 2 P 2 0 7 may give Mössbauer signals influencing the low-and highvelocity absorption profiles. However, the Mössbauer spectra for conceivable impurities are well known, and so are the X-ray diffraction data of Fe 2 P 2 0 7 (Stefanidis and Nord, 1982). Thus the maximum total amounts of impurities can be estimated to about 2 weight %.…”

Section: Figmentioning

confidence: 99%

Cation distributions in (Fe₁ _-zMe_z)₃(PO₄)₂ graftonite-type solid solutions determined by Mössbauer spectroscopy

Nord¹,

Ericsson²

1982

Zeitschrift Für Kristallographie - Crystalline Materials

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Solid solutions of Me 3 (P0 4 ) 2 in Fe 3 (P0 4 ) 2 , with the graftonitetype structure, have been prepared and equilibrated at 1070 Κ (Me = Mg, Ca, Co, Ni, Zn, or Cd). The (Fe! _ 2 Afe z ) 3 (P0 4 ) 2 phases are isomorphous with Fe 3 (P0 4 ) 2 as well as with the mineral graftonite. Accurate unit cell dimensions (P2 1 /c) have been obtained from Guinier-Hägg photographic data. The unit cell volume is strongly correlated with the amount and size of the incorporated Me 2 + cation. Mössbauer spectroscopy ( 57 Fe) has been used to determine the cation distribution of Fe 2 + and Me 2 + between the three distinct cationic environments in the structure : one octahedron and two fivecoordinated polyhedra, all distorted. The order of preference for five-over six-coordination may be given as Zn 2+ > Fe 2 + , Mg 2+ , Co 2+ , Ni 2+ > Ca 2+ > Mn 2+ > Cd 2 + .

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The crystal structure of iron(II) diphosphate, Fe₂P₂O₇

Cited by 22 publications

References 7 publications

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

How to avoid unnecessarily low symmetry in crystal structure determinations

Cation distributions in (Fe₁ _-zMe_z)₃(PO₄)₂ graftonite-type solid solutions determined by Mössbauer spectroscopy

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The crystal structure of iron(II) diphosphate, Fe2P2O7

Cited by 22 publications

References 7 publications

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

CRYSTAL STRUCTURE OF -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

How to avoid unnecessarily low symmetry in crystal structure determinations

Cation distributions in (Fe1 -zMez)3(PO4)2 graftonite-type solid solutions determined by Mössbauer spectroscopy

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The crystal structure of iron(II) diphosphate, Fe₂P₂O₇

Cation distributions in (Fe₁ _-zMe_z)₃(PO₄)₂ graftonite-type solid solutions determined by Mössbauer spectroscopy