Le nitrate double NaRb2(NO3)3, composé intermédiaire du système binaire isobare NaNO3 + RbNO3: études thermiques et cristallographiques

Acta Crystallographica Section E: Crystallographic Communications

Driss, M.¹  Hellali, D.⁴  Zamali, H.⁵  Ksiksi, N.⁵  Guesmi, A.⁶ 

[1] de Tunis El Manar, Facultéde Tunis El Manar, Institut Prédes Sciences, Laboratoire de Matédes Sciences, Laboratoire de Thermodynamique appliquéUniversitée, El Manar II, 2092 Tunis, Tunisie;nieurs d'El Manar, El Manar II, 2092 Tunis, Tunisie;paratoire aux Etudes d'Ingériaux et Cristallochimie, El Manar II, 2092 Tunis, Tunisie

关键词: CRYSTAL STRUCTURE;    NANO3 + RBNO3 PHASE DIAGRAM;    BOND-VALENCE SUM;    CHARGE-DISTRIBUTION METHOD;   

DOI  :  10.1107/S2056989015006532

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

Crystallographic and thermodynamic investigations of the binary (NaNO3 + RbNO3) phase diagram at atmospheric pressure reveal the existence of an inter­mediate compound NaRb2(NO3)3 (sodium dirubidium trinitrate) previously predicted and now reported experimentally for the first time. According to a DSC analysis, the compound exhibits three allotropic forms. In its low-temperature allotropic form (α form, ortho­rhom­bic) there are two Rb (m.. site symmetry) and one Na (m..) independent crystallographic positions and three planar nitrate groups. The bond-valence-sum calculations for all atoms agree well with their oxidation states. The Rb cations are located in the (100) plane at x = ½ with 11 oxygen coordination. The Na ones are in the same plane at x = 0 and are coordinated to eight O atoms from six nitrate groups. The charge-distribution method has been used to evaluate the degree of distortion of the alkali polyhedra.

【 授权许可】

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