Materials Data on Eu2Ta2O7 by Materials Project
Eu2Ta2O7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. There are four shorter (2.49 Å) and two longer (2.52 Å) Eu–O bond lengths. In the second Eu2+ site, Eu2+ is bonded to twelve O2- atoms to form EuO12 cuboctahedra that share corners with six equivalent EuO12 cuboctahedra, faces with four equivalent EuO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Eu–O bond distances ranging from 2.63–2.86 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra and faces with two equivalent EuO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 9–14°. There are a spread of Ta–O bond distances ranging from 1.91–2.12 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with six equivalent EuO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–12°. There are a spread of Ta–O bond distances ranging from 1.94–2.06 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Eu2+ and one Ta5+ atom to form a mixture of distorted corner and edge-sharing OEu3Ta tetrahedra. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Eu2+ and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Eu2+ and two Ta5+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to three equivalent Eu2+ and two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Eu2+ and two equivalent Ta5+ atoms.