Le nitrate double NaRb2(NO3)3, compose intermediaire du systeme binaire isobare NaNO3 + RbNO3: etudes thermiques et cristallographiques.

ABSTRACT: 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 (? 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.

SUBMITTER: Ksiksi N 

PROVIDER: S-EPMC4420088 | biostudies-other | 2015 May

REPOSITORIES: biostudies-other