Acta Cryst. (2001). E57, i90-i91 [ doi:10.1107/S160053680101501X ]
Abstract: A hexagonal modification (P63mc) of (NH4)2SiF6 was grown accidentally. This new modification has the unit-cell c parameter doubled with respect to a previously reported trigonal form (Pm1) of the title compound. The H atoms in the present structure are ordered. Three or even four F atoms are hydrogen-bond acceptors for each H atom. The structure is isostructural with modifications of (NH4)2MnF6, K2GeF6 and Rb2GeF6.
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