Materials Data on Ca4Mn2O7 by Materials Project
Ca4Mn2O7 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.95 Å. Mn3+ is bonded to five O2- atoms to form corner-sharing MnO5 square pyramids. There are a spread of Mn–O bond distances ranging from 1.88–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ca2+ and two equivalent Mn3+ atoms to form a mixture of distorted edge and corner-sharing OCa4Mn2 octahedra. In the second O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Mn3+ atoms to form distorted OCa2Mn2 tetrahedra that share corners with two equivalent OCa4Mn2 octahedra, corners with two equivalent OCa2Mn2 tetrahedra, and an edgeedge with one OCa4Mn2 octahedra. The corner-sharing octahedra tilt angles range from 18–79°. In the third O2- site, O2- is bonded in a 6-coordinate geometry to five equivalent Ca2+ and one Mn3+ atom.