Structure cristalline de Pb3Mn7O15

Darriet, B.; Devalette, Michel; Latourrette, B.

doi:10.1107/s0567740878011528

Cited by 24 publications

(29 citation statements)

References 1 publication

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“…The structure of this compound was described in the orthorhombic space group Cmc21, with a = 17.28 (1), b = 9.98 (1), c = 13.55 (1)A, and refined to an R of 0.047 for 904 reflections with I > 1.5o(1) (Darriet, Devalette & Latourrette, 1978;DDL). It can be better described in Cmcm.…”

Section: Pb3mn70~5mentioning

confidence: 99%

Some additional changes in space groups of published crystal structures

Marsh¹,

Herbstein²

1983

Acta Crystallogr Sect B

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Section: Pb3mn70~5mentioning

confidence: 99%

Some additional changes in space groups of published crystal structures

Marsh¹,

Herbstein²

1983

Acta Crystallogr Sect B

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“…Attempting to read in a single step the space-group symmetry, conventional cell edges and proper origin of coordinates off a structure plot is a difficult art, especially with inorganic structures and high symmetries. See for example the succession of papers on the crystallographic description of Pb3Mn7015: Darriet, Devalette & Latourrette (1978), Marsh & Herbstein (1983), Le Page & Calvert (1984), Le Page (1987) and Holtstam, Lindqvist, Johnsson & Norrestam (1991 ). A number of wrong space-group assignments in descriptions of simple inorganic structure types, where all atoms were already in special positions with all coordinates fixed by the space-group symmetry, remained unnoticed for years until unquestionable additional symmetry was disclosed by Cenzual, Gelato, Penzo & Parth6 (1991) with use of the MISSYM program.…”

Section: Discussionmentioning

confidence: 99%

Derivation of conventional crystallographic descriptions of new phases from results of ab initio inorganic structure modelling

Page¹,

Klug²,

Tseb³

1996

J Appl Cryst

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The results of ab initio inorganic structure modelling are often in the form of Cartesian coordinates of atoms in a large, periodical and in general oblique simulation box containing hundreds to thousands of atoms. The contents of that box may correspond to a single crystal, a twin, a mixture of phases or a disordered block of matter. The problem of extracting corresponding crystallographic descriptions for single-crystal regions in the box, a necessary step in view of full quantum calculations and publication, is different from the familiar problem of extracting crystal symmetry and structure from experimental diffracted intensity data. The deductive computeraided method developed at the National Research Council of Canada over the years is based on eye identification of three pairs of atoms related by conjugate translations in the same single-crystal region on a stereo plot, followed by derivation of fractional coordinates for the atomic content of the corresponding primitive cell. Running this data through the MISSYM program discloses potential symmetry elements of the structure, with their corresponding crystallographic directions. These elements are then critically examined and accepted either as symmetry or pseudosyrnmetry on the basis of comparison of coordinate deviations between related atoms with the expected magnitude of thermal motion. All calculations described here can be performed with the NRCVAX system of programs.

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“…Crystals in bold and italics show similar amorphous structure for the TeO 3 -isolated and α-TeO 4 units, respectively (see Figure 3.2). * The methods listed here were those that proved successful by Sakida et al (Sakida et al, 1999a (1) 600(M)/1 → RT (2) 500(4) → RT (Darriet et al, 1972) *Simulated patterns were generated with JADE with a 10 Å crystallite size and 0% strain M: melting (time = 1-2 hr) RT: room temperature with a cooling rate of 1°C/min?) QU: quenched Figure 3.2.…”

Section: Tellurite Crystal Fabricationmentioning

confidence: 99%

Alternative Electrochemical Salt Waste Forms, Summary of FY/CY2011 Results

Riley¹,

McCloy²,

Crum³

et al. 2011

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SUMMARYThe Fuel Cycle Research and Development Program, sponsored by the U.S. Department of Energy Office of Nuclear Energy, is currently investigating alternative waste forms for wastes generated from the reprocessing of nuclear fuel. One such waste results from an electrochemical separations process, called the "Echem" process, in molten KCl-LiCl salt as a spent salt containing alkali, alkaline earth, lanthanide halides and a small quantities of actinide halides where the primary anion is chloride with small quantities of iodide. Pacific Northwest National Laboratory (PNNL) is investigating two candidate waste forms for the Echem spent-salt, high-halide minerals (i.e., sodalite and cancrinite) and tellurite (TeO 2 )-based glasses. Both of these candidates showed promise in FY2009 and FY2010 with a simplified nonradioactive simulant of the Echem waste. Further testing was performed on these waste forms in the fiscal (FY) and calendar (CY) year of 2011 to investigate the possibility of their use in a sustainable fuel cycle. This report summarizes the results of FY/CY2011 efforts.The chemical durability results for the tellurite glasses in FY2010 revealed a wide variety of waste form performance in these materials. The most promising glass studied was a lead-tellurite glass formulation with the Echem salt simulant. This glass showed very good chemical durability with a normalized release for sodium of 0.478 g/m 2 following a seven-day leaching test. With this in mind, the following studies were undertaken in FY/CY2011 to further investigate and optimize this type of glass as a potential waste form: 1) Expanded study on lead-tellurite glasses. The lead-tellurite glass system was further investigated in FY/CY2011 to determine the waste-loading limits and assess the tellurium-oxygen bonding structure as a function of waste loading with Raman spectroscopy and X-ray diffraction. Te-O bonding in tellurite glasses is quite complex; at least eight different structures have been presented in the literature and typically include α-TeO 4 , β-TeO 4 , TeO 3+1 , and TeO 3 structures (the α/β notation denotes the way that the TeO 4 species bond to one another, and the number after the "O" denotes the number of oxygens bonded to the central Te atom in that species). We also investigated some of the other waste-form related properties of the lead-tellurite glasses, such as the thermal diffusivity, glass transition temperature, crystallization temperature, melting temperature, and mass loss as a function of temperature. The structural investigation revealed that the medium-range order in the glass decreased and the tellurite network was depolymerized as the waste fraction was increased. It was apparent that glass-network breaking was predominantly caused by the additions of the waste cations and that the presence of chloride may have actually caused some repolymerization of the network by scavenging alkali and preventing it from acting as a network modifier. At the highest waste loadings, the glass became phaseseparated, resulting...

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Structure cristalline de Pb₃Mn₇O₁₅

Cited by 24 publications

References 1 publication

Some additional changes in space groups of published crystal structures

Some additional changes in space groups of published crystal structures

Derivation of conventional crystallographic descriptions of new phases from results of ab initio inorganic structure modelling

Alternative Electrochemical Salt Waste Forms, Summary of FY/CY2011 Results

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