Acta Cryst. (2014). C70, 256-259 [ doi:10.1107/S2053229614002423 ]
Synopsis: The directionality of (Al,Si)O4 tetrahedra within six-membered rings (S6R) could not be defined in disordered kalsilite, i.e. equal probability for U or D directionality [free apex pointing up (U) or down (D)] of (Al,Si)O4 tetrahedra is established. In ordered kalsilite, S6R of (Al,Si)O4 tetrahedra are characterized with the UDUDUD sequence of the directionality of the tetrahedra.
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