Structure cristalline du solvate Hg Br2• C4H8O

The crystal structure of solvate HgBr₂ • C₄H₈O has been determined from the intensities of 590 reflexions (hk0 to hk3). They had been registered with a Weissenberg camera. The final R factor is 0.096. The structure consists of groups in which HgBr₂ chains parallel to c are linked to tetrahydrofuran rings by Hg…O = 2.67 Å. HgBr₂ molecules are slightly bent (Hg-Br = 2.475 Å, Br-Hg-Br = 174°6). Mercury atoms have octahedral surroundings. The chains of strongly bonded HgBr₂ have the same structure as in pure HgBr₂.La structure cristalline a été déterminée à partir des intensités de 590 taches intégrées (hk0 à hk3) recueillies à l'aide d'une chambre de Weissenberg. Le facteur R final est égal à 0,096. La structure est formée de groupes de deux chaînes HgBr₂ parallèles à c et reliées aux cycles tétrahydrofuranne par Hg…O = 2,67 Å. Les molécules HgBr₂ sont légèrement coudées (Hg-Br = 2,475 Å, Br-Hg-Br = 174°6). L'entourage des atomes de mercure est octaédrique. Les chaînes de liaisons fortes HgBr₂ ont la même structure que celles de HgBr₂ pur.Frey Michel, Leligny Henri, Ledésert Maryannick. Structure cristalline du solvate Hg Br2• C4H8O. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 94, 5-6, 1971. pp. 467-470

Structural investigation of composite phases Ba1+x[(NaxMn1−x)O3] with x= 2/7, 5/17 and 1/3 ; exotic Mn4.5+ valence in perovskite-like structure

International audienceStructural models are proposed for three composite compounds of chemical formula Ba 1+x[(NaxMn1-x)O3] (x2/7, 5/17 and 1/3) by single crystal X-ray diffraction ; super space formalism is used to obtain an unified description of the three phases. The [(NaxMn1-x)O3] framework is built up from the stacking of face sharing MnO6 octahedra and NaO6 trigonal prisms. The displacive modulations relating to these metallic columns were particularly difficult to modelize. Thus a model, including both discontinuous crenel-like functions for Ba atoms and continuous atomic strings for the Mn/Na sites has finally been retained. The large displacement of the oxygen atoms ( ±0.7 ° A) in comparison with that observed for related compounds ( ±0.3 ° A) makes it a direct consequence of the Na+ alkali insertion inside the trigonal prisms. Owing to this insertion, the Mn atoms exhibit, in the three phases, an ”exotic” oxidation state of about + 4.5

Structural investigation of composite phases Ba1+x[(NaxMn1−x)O3] with x= 2/7, 5/17 and 1/3 ; exotic Mn4.5+ valence in perovskite-like structure

International audienceStructural models are proposed for three composite compounds of chemical formula Ba 1+x[(NaxMn1-x)O3] (x2/7, 5/17 and 1/3) by single crystal X-ray diffraction ; super space formalism is used to obtain an unified description of the three phases. The [(NaxMn1-x)O3] framework is built up from the stacking of face sharing MnO6 octahedra and NaO6 trigonal prisms. The displacive modulations relating to these metallic columns were particularly difficult to modelize. Thus a model, including both discontinuous crenel-like functions for Ba atoms and continuous atomic strings for the Mn/Na sites has finally been retained. The large displacement of the oxygen atoms ( ±0.7 ° A) in comparison with that observed for related compounds ( ±0.3 ° A) makes it a direct consequence of the Na+ alkali insertion inside the trigonal prisms. Owing to this insertion, the Mn atoms exhibit, in the three phases, an ”exotic” oxidation state of about + 4.5