Materials Data on Cr2H8N2O7 by Materials Project
(NH4)2Cr2O7 is beta Plutonium-derived structured and crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight ammonium molecules and four Cr2O7 clusters. In each Cr2O7 cluster, Cr6+ is bonded to four O2- atoms to form corner-sharing CrO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.62–1.79 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Cr6+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Cr6+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom.