Materials Data on Ca4UAl2(SiO5)3 by Materials Project

Abstract

Ca4UAl2(SiO5)3 is (Cubic) Perovskite-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with twelve CaO12 cuboctahedra, faces with three equivalent CaO12 cuboctahedra, faces with three equivalent UO12 cuboctahedra, faces with four equivalent AlO6 octahedra, and faces with four SiO6 octahedra. There are three shorter (2.58 Å) and nine longer (2.60 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with three equivalent UO12 cuboctahedra, corners with nine CaO12 cuboctahedra, faces with six CaO12 cuboctahedra, a faceface with one AlO6 octahedra, and faces with seven SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.57–2.62 Å. U4+ is bonded to twelve O2- atoms to form UO12 cuboctahedra that share corners with six equivalent CaO12 cuboctahedra, corners with six equivalent UO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, faces with two equivalent SiO6 octahedra, and faces with six equivalent AlO6 octahedra. There are six shorter (2.56 Å) and six longer (2.59 Å) U–O bond lengths. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent AlO6 octahedra, corners with three equivalent SiO6 octahedra, faces with three equivalent UO12 cuboctahedra, and faces with five CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There is three shorter (1.85 Å) and three longer (1.88 Å) Al–O bond length. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with three equivalent AlO6 octahedra, corners with three equivalent SiO6 octahedra, a faceface with one UO12 cuboctahedra, and faces with seven CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There is three shorter (1.78 Å) and three longer (1.82 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to six equivalent O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight CaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Si–O bond lengths are 1.82 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two equivalent Ca2+, two equivalent U4+, and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to three Ca2+, one U4+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to four Ca2+ and two Si4+ atoms.