DOE OSTI2020
(NH4)2BeF4 is Silicon tetrafluoride-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four ammonium molecules and four BeNH4F4 clusters. In each BeNH4F4 cluster, Be2+ is bonded in a tetrahedral geometry to four F1- atoms. There is two shorter (1.56 Å) and two longer (1.57 Å) Be–F bond length. N3- is bonded in a tetrahedral geometry to four H1+ atoms. There are a spread of N–H bond distances ranging from 1.02–1.06 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to one N3- and one F1- atom. The H–F bond length is 1.59 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a bent 120 degrees geometry to one Be2+ and one H1+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Be2+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Be2+ atom.