Le nitrate double NaRb2(NO3)3, composé intermédiaire du système binaire isobare NaNO3 + RbNO3: études thermiques et cristallographiques
نویسندگان
چکیده
Crystallographic and thermodynamic investigations of the binary (NaNO3 + RbNO3) phase diagram at atmospheric pressure reveal the existence of an inter-mediate 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, ortho-rhom-bic) 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.
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عنوان ژورنال:
دوره 71 شماره
صفحات -
تاریخ انتشار 2015