Materials Data on Pr3(Al2Si3)2 by Materials Project

Abstract

Pr3Al4Si6 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are two inequivalent Pr4+ sites. In the first Pr4+ site, Pr4+ is bonded in a 9-coordinate geometry to nine Si4- atoms. There are a spread of Pr–Si bond distances ranging from 3.10–3.19 Å. In the second Pr4+ site, Pr4+ is bonded to six equivalent Si4- atoms to form PrSi6 octahedra that share corners with twelve AlSi4 tetrahedra, edges with six equivalent PrSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Pr–Si bond lengths are 3.08 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four Si4- atoms to form AlSi4 tetrahedra that share corners with three equivalent PrSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are three shorter (2.51 Å) and one longer (2.55 Å) Al–Si bond lengths. In the second Al3+ site, Al3+ is bonded to four Si4- atoms to form AlSi4 tetrahedra that share corners with three equivalent PrSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent PrSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedral tilt angles are 23°. There are three shorter (2.51 Å) and one longer (2.55 Å) Al–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded to three equivalent Pr4+ and four Al3+ atoms to form a mixture of distorted corner and edge-sharing SiPr3Al4 pentagonal bipyramids. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to six equivalent Pr4+ and three equivalent Si4- atoms. All Si–Si bond lengths are 2.43 Å. In the third Si4- site, Si4- is bonded in a 7-coordinate geometry to three equivalent Pr4+ and four Al3+ atoms.