DOE OSTI2020
Sr3Mo2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 1-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.41–2.86 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent MoO6 octahedra. There are four shorter (2.85 Å) and eight longer (2.89 Å) Sr–O bond lengths. Mo4+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with five equivalent MoO6 octahedra and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mo–O bond distances ranging from 2.01–2.12 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sr2+ and two equivalent Mo4+ atoms to form a mixture of distorted edge, face, and corner-sharing OSr4Mo2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°. In the second O2- site, O2- is bonded to five equivalent Sr2+ and one Mo4+ atom to form distorted OSr5Mo octahedra that share corners with seventeen OSr4Mo2 octahedra, edges with eight equivalent OSr5Mo octahedra, and faces with four equivalent OSr4Mo2 octahedra. The corner-sharing octahedra tilt angles range from 0–56°. In the third O2- site, O2- is bonded to four equivalent Sr2+ and two equivalent Mo4+ atoms to form a mixture of distorted edge, face, and corner-sharing OSr4Mo2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°. In the fourth O2- site, O2- is bonded to four equivalent Sr2+ and two equivalent Mo4+ atoms to form a mixture of distorted edge, face, and corner-sharing OSr4Mo2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°. All O–Sr bond lengths are 2.85 Å. Both O–Mo bond lengths are 2.11 Å.