Materials Data on Mg2Ta4O9 by Materials Project

Abstract

Mg2Ta4O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with nine TaO6 octahedra, edges with three equivalent TaO6 octahedra, and a faceface with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are three shorter (1.99 Å) and three longer (2.16 Å) Mg–O bond lengths. There are two inequivalent Ta+3.50+ sites. In the first Ta+3.50+ site, Ta+3.50+ is bonded to six equivalent O2- atoms to form TaO6 octahedra that share corners with three equivalent TaO6 octahedra, corners with six equivalent MgO6 octahedra, edges with three equivalent TaO6 octahedra, and a faceface with one TaO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are three shorter (2.11 Å) and three longer (2.19 Å) Ta–O bond lengths. In the second Ta+3.50+ site, Ta+3.50+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent MgO6 octahedra, corners with six TaO6 octahedra, edges with three equivalent MgO6 octahedra, and a faceface with one TaO6 octahedra. The corner-sharing octahedra tilt angles range from 48–57°. There are three shorter (2.06 Å) and three longer (2.14 Å) Ta–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Ta+3.50+ atoms. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Ta+3.50+ atoms to form a mixture of distorted edge and corner-sharing OMg2Ta2 trigonal pyramids.