Crystal structure of Fe2P2O7

Hoggins, J. T.; Swinnea, J. S.; Steinfink, H.

doi:10.1016/0022-4596(83)90019-1

Cited by 55 publications

(28 citation statements)

References 6 publications

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“…The origin of this large linear term was suggested to result from a density of localized states associated with oxygen vacancies that exist in these layered compounds. Fe 2 P 2 O 7 has a similar layered structure that contains distorted close-packed layers of oxygen atoms [52] or two-dimensional zigzag sheets formed by FeO 6 octahedra [31] implying the large electronic term is likely due to the oxygen vacancies formed in this layered structure.…”

Section: Discussionmentioning

confidence: 99%

Low temperature heat capacity Study of Fe(PO3)3 and Fe2P2O7

Shi

Zhang

Schlesinger

et al. 2013

The Journal of Chemical Thermodynamics

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Section: Discussionmentioning

confidence: 99%

Low temperature heat capacity Study of Fe(PO3)3 and Fe2P2O7

Shi

Zhang

Schlesinger

et al. 2013

The Journal of Chemical Thermodynamics

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“…Stefanidis & Nord chose the noncentrosymmetric space group because the statistical N(z) test after Howells, Phillips & Rogers (1950) gave an unequivocally acentric result. Hoggins et al (1983), however, report that their data agree closely with a centrosymmetric distribution. It is unlikely that Fe2P207 exists in two modifications with essentially identical cell constants, but one with, the other without an inversion center.…”

Section: (Q) Diiron(ii) Diphosphate Fe2p207mentioning

confidence: 86%

“…Shortly thereafter Hoggins, Swinnea & Steinfink (1983) published a structure determination of the same compound in a centrosymmetric triclinic setting. Stefanidis & Nord chose the noncentrosymmetric space group because the statistical N(z) test after Howells, Phillips & Rogers (1950) gave an unequivocally acentric result.…”

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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High‐Voltage Pyrophosphate Cathodes

Barpanda

Nishimura

Yamada

2012

Advanced Energy Materials

223

146

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The quest to explore and to discover novel cathode materials is key to sustaining the progress of Li-ion rechargeable batteries. It has encouraged materials' chemists to design and develop a variety of polyanionic compounds. This paper reports and summarizes recent progress in the development of alkali metal pyrophosphate based cathode materials for battery applications. It points out that the pyrophosphate-based polyanionic-framework materials offer a rich crystal chemistry, ease of synthesis and robust structure offering good alkali-ion mobility. Thus, they can form a promising class of cathode materials both for lithium-and sodium-ion secondary batteries. In the Perspectives section, it is speculated that keen study of the myriad of pyrophosphate phases, selective screening and design of key pyrophosphate compounds with open frameworks and optimizing those compounds with nanosizing and carbon coating can lead to breakthroughs in the realization of commercially viable high-voltage Li-ion and Na-ion pyrophosphate cathodes.

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Crystal structure of Fe2P2O7

Cited by 55 publications

References 6 publications

Low temperature heat capacity Study of Fe(PO3)3 and Fe2P2O7

Low temperature heat capacity Study of Fe(PO3)3 and Fe2P2O7

How to avoid unnecessarily low symmetry in crystal structure determinations

High‐Voltage Pyrophosphate Cathodes

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