DOI: 10.17188/1733838
title: Materials Data on Na2Cr2H2O7 by Materials Project

description: Na2Cr2O7H2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional and consists of eight hydrogen molecules and one Na2Cr2O7 framework. In the Na2Cr2O7 framework, there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with five CrO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.24–2.53 Å. In the second Na1+ site, Na1+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.28–2.34 Å. In the third Na1+ site, Na1+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.25–2.39 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with five CrO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.32–2.43 Å. There are four inequivalent Cr5+ sites. In the first Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and corners with two NaO4 trigonal pyramids. There are a spread of Cr–O bond distances ranging from 1.63–1.79 Å. In the second Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and a cornercorner with one NaO4 trigonal pyramid. There are a spread of Cr–O bond distances ranging from 1.62–1.80 Å. In the third Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and corners with three NaO4 trigonal pyramids. There are a spread of Cr–O bond distances ranging from 1.62–1.81 Å. In the fourth Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and corners with four NaO4 trigonal pyramids. There is three shorter (1.63 Å) and one longer (1.80 Å) Cr–O bond length. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Na1+ and one Cr5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+ and two Cr5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one Cr5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the ninth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+ and two Cr5+ atoms. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and one Cr5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one Cr5+ atom. In the thirteenth O2- site, O2- is bonded in a trigonal planar geometry to two Na1+ and one Cr5+ atom. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Na1+ and one Cr5+ atom.