DOE OSTI2020
Eu2As2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Eu–O bond lengths are 2.69 Å. In the second Eu3+ site, Eu3+ is bonded to twelve O2- atoms to form EuO12 cuboctahedra that share corners with four equivalent EuO12 cuboctahedra, faces with four equivalent EuO12 cuboctahedra, and faces with eight equivalent AsO5 square pyramids. There are eight shorter (2.85 Å) and four longer (2.96 Å) Eu–O bond lengths. As2+ is bonded to five O2- atoms to form AsO5 square pyramids that share corners with five equivalent AsO5 square pyramids and faces with four equivalent EuO12 cuboctahedra. There are one shorter (1.93 Å) and four longer (2.09 Å) As–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four Eu3+ and two equivalent As2+ atoms to form a mixture of distorted edge, face, and corner-sharing OEu4As2 octahedra. The corner-sharing octahedra tilt angles range from 0–67°. In the second O2- site, O2- is bonded in a linear geometry to four equivalent Eu3+ and two equivalent As2+ atoms.