The low-temperature behavior of balliranoite (CAN topology): An in situ single-crystal X-ray diffraction study

The thermoelastic behavior and structural evolution of a natural balliranoite (Na4.47Ca2.86K0.11)(Si5.96Al6.04O24)Cl2.03(CO3)0.78(SO4)0.33, a = 12.6701(3) Å, c = 5.3178(1) Å and V = 739.30(3) Å3, space group P63, the CO32- analogue of davyne, a cancrinite-group mineral, have been studied within the range 108 ⩽ T (K) ⩽ 293 by in situ single-crystal X-ray diffraction. No evidences of phase transition or change of the “compressional” behavior have been observed. The refined volume thermal expansion coefficient is αV = 4.6(4)∗10−5 K−1, whereas the refined unit-cell edges linear thermal expansion coefficients are αa = 1.4(2)∗10−5 K−1 and αc = 1.7(2)∗10−5 K−1. The structural evolution at T ⩽ 293 K is driven by the rotation of the rigid TO4 framework tetrahedra. A description of the main deformation mechanisms is carried out along with a comparison with the cancrinite behavior at the same temperature conditions. Significant differences pertaining to the mechanisms acting on the (0 0 0 1) plane are observed between these isotypic materials. These results suggest that the coordination environment of cations within the can unit could influence the magnitude of the [CAN] framework deformation at low-T.

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► Thermoelastic behavior and structural evolution of balliranoite were studied at 108 ⩽ T (K) ⩽ 293.
► No phase transition or change of the compressional behavior were observed.
► Thermal expansion coefficient is similar to that of cancrinite.
► Different deformation mechanisms were observed between balliranoite and cancrinite.
► The nature of cations in the ε-cage influences the deformation mechanisms magnitude.