Materials Data on U4SiN3 by Materials Project

Abstract

U4SiN3 is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are five inequivalent U+3.25+ sites. In the first U+3.25+ site, U+3.25+ is bonded to two equivalent Si4- and four N3- atoms to form USi2N4 octahedra that share corners with six USi2N4 octahedra and edges with twelve USiN5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both U–Si bond lengths are 2.56 Å. There are two shorter (2.48 Å) and two longer (2.56 Å) U–N bond lengths. In the second U+3.25+ site, U+3.25+ is bonded to one Si4- and five N3- atoms to form distorted USiN5 octahedra that share corners with six equivalent USiN5 octahedra and edges with twelve USi2N4 octahedra. The corner-sharing octahedra tilt angles range from 0–9°. The U–Si bond length is 2.68 Å. There are one shorter (2.29 Å) and four longer (2.57 Å) U–N bond lengths. In the third U+3.25+ site, U+3.25+ is bonded to two equivalent Si4- and four N3- atoms to form a mixture of edge and corner-sharing USi2N4 octahedra. The corner-sharing octahedral tilt angles are 0°. Both U–Si bond lengths are 2.56 Å. There are two shorter (2.48 Å) and two longer (2.56 Å) U–N bond lengths. In the fourth U+3.25+ site, U+3.25+ is bonded to two equivalent Si4- and four N3- atoms to form USi2N4 octahedra that share corners with six USi2N4 octahedra and edges with twelve USiN5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both U–Si bond lengths are 2.56 Å. There are two shorter (2.48 Å) and two longer (2.56 Å) U–N bond lengths. In the fifth U+3.25+ site, U+3.25+ is bonded to two equivalent Si4- and four N3- atoms to form USi2N4 octahedra that share corners with six USi2N4 octahedra and edges with twelve USiN5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both U–Si bond lengths are 2.56 Å. There are two shorter (2.48 Å) and two longer (2.56 Å) U–N bond lengths. Si4- is bonded to six U+3.25+ atoms to form SiU6 octahedra that share corners with two equivalent NU6 octahedra, corners with four equivalent SiU6 octahedra, and edges with twelve NU6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to six U+3.25+ atoms to form NU6 octahedra that share corners with six equivalent NU6 octahedra, edges with four equivalent SiU6 octahedra, and edges with eight NU6 octahedra. The corner-sharing octahedra tilt angles range from 0–9°. In the second N3- site, N3- is bonded to six U+3.25+ atoms to form NU6 octahedra that share corners with two equivalent SiU6 octahedra, corners with four equivalent NU6 octahedra, edges with four equivalent SiU6 octahedra, and edges with eight equivalent NU6 octahedra. The corner-sharing octahedral tilt angles are 0°.