Materials Data on Er2Ti2O7 by Materials Project
Er2Ti2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Er3+ is bonded to eight O2- atoms to form distorted ErO8 hexagonal bipyramids that share edges with six equivalent ErO8 hexagonal bipyramids and edges with six equivalent TiO6 octahedra. There are two shorter (2.19 Å) and six longer (2.47 Å) Er–O bond lengths. Ti4+ is bonded to six equivalent O2- atoms to form TiO6 octahedra that share corners with six equivalent TiO6 octahedra and edges with six equivalent ErO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. All Ti–O bond lengths are 1.97 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Er3+ atoms to form corner-sharing OEr4 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Er3+ and two equivalent Ti4+ atoms.