DOE OSTI2020
KMgAs(H6O5)2 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. K1+ is bonded in a 1-coordinate geometry to two equivalent H1+ and six O2- atoms. Both K–H bond lengths are 2.96 Å. There are a spread of K–O bond distances ranging from 2.87–3.03 Å. Mg2+ is bonded in an octahedral geometry to six O2- atoms. There are three shorter (2.09 Å) and three longer (2.15 Å) Mg–O bond lengths. As5+ is bonded in a tetrahedral geometry to four O2- atoms. There is one shorter (1.72 Å) and three longer (1.73 Å) As–O bond length. There are six inequivalent H1+ sites. In the first 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 (1.67 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one K1+ and one O2- atom. The H–O bond length is 0.97 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.73 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.63 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.61 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.59 Å) H–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal non-coplanar geometry to one As5+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded to one As5+ and three H1+ atoms to form distorted corner-sharing OAsH3 tetrahedra. In the third O2- site, O2- is bonded in a distorted water-like geometry to one K1+, one Mg2+, and two H1+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Mg2+, and two H1+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent H1+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Mg2+, and two equivalent H1+ atoms. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one K1+, one As5+, and two equivalent H1+ atoms.