U4SiN3 is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent Si(1), two equivalent N(1), and two equivalent N(2) atoms to form USi2N4 octahedra that share corners with six equivalent U(1)Si2N4 octahedra, edges with four equivalent U(1)Si2N4 octahedra, and edges with eight equivalent U(2)SiN5 octahedra. The corner-sharing octahedra are not tilted. In the second U site, U(2) is bonded to one Si(1), one N(2), and four equivalent N(1) atoms to form distorted USiN5 octahedra that share corners with six equivalent U(2)SiN5 octahedra, edges with four equivalent U(2)SiN5 octahedra, and edges with eight equivalent U(1)Si2N4 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. Si(1) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form SiU6 octahedra that share corners with two equivalent N(2)U6 octahedra, corners with four equivalent Si(1)U6 octahedra, edges with four equivalent N(2)U6 octahedra, and edges with eight equivalent N(1)U6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent N sites. In the first N site, N(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form NU6 octahedra that share corners with six equivalent N(1)U6 octahedra, edges with four equivalent Si(1)U6 octahedra, edges with four equivalent N(1)U6 octahedra, and edges with four equivalent N(2)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second N site, N(2) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form NU6 octahedra that share corners with two equivalent Si(1)U6 octahedra, corners with four equivalent N(2)U6 octahedra, edges with four equivalent Si(1)U6 octahedra, and edges with eight equivalent N(1)U6 octahedra. The corner-sharing octahedra are not tilted.
U4SiN3 is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent Si(1), two equivalent N(1), and two equivalent N(2) atoms to form USi2N4 octahedra that share corners with six equivalent U(1)Si2N4 octahedra, edges with four equivalent U(1)Si2N4 octahedra, and edges with eight equivalent U(2)SiN5 octahedra. The corner-sharing octahedra are not tilted. Both U(1)-Si(1) bond lengths are 2.56 Å. Both U(1)-N(1) bond lengths are 2.48 Å. Both U(1)-N(2) bond lengths are 2.56 Å. In the second U site, U(2) is bonded to one Si(1), one N(2), and four equivalent N(1) atoms to form distorted USiN5 octahedra that share corners with six equivalent U(2)SiN5 octahedra, edges with four equivalent U(2)SiN5 octahedra, and edges with eight equivalent U(1)Si2N4 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. The U(2)-Si(1) bond length is 2.68 Å. The U(2)-N(2) bond length is 2.29 Å. All U(2)-N(1) bond lengths are 2.57 Å. Si(1) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form SiU6 octahedra that share corners with two equivalent N(2)U6 octahedra, corners with four equivalent Si(1)U6 octahedra, edges with four equivalent N(2)U6 octahedra, and edges with eight equivalent N(1)U6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent N sites. In the first N site, N(1) is bonded to two equivalent U(1) and four equivalent U(2) atoms to form NU6 octahedra that share corners with six equivalent N(1)U6 octahedra, edges with four equivalent Si(1)U6 octahedra, edges with four equivalent N(1)U6 octahedra, and edges with four equivalent N(2)U6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second N site, N(2) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form NU6 octahedra that share corners with two equivalent Si(1)U6 octahedra, corners with four equivalent N(2)U6 octahedra, edges with four equivalent Si(1)U6 octahedra, and edges with eight equivalent N(1)U6 octahedra. The corner-sharing octahedra are not tilted.