DOE OSTI2020
NH4H2PO4 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional and consists of four ammonium molecules and one H2PO4 framework. In the H2PO4 framework, P5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of P–O bond distances ranging from 1.51–1.60 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.54 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.66 Å) H–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H1+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one P5+ and two H1+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom.