Sr3(SiAs2)2 crystallizes in the monoclinic C2/c space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(2)As6 octahedra, corners with two equivalent Sr(3)As6 octahedra, corners with four equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(1)As6 octahedra, edges with three equivalent Sr(3)As6 octahedra, edges with four equivalent Sr(2)As6 octahedra, and edges with two equivalent Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 4-12°. In the second Sr site, Sr(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent Sr(3)As6 octahedra, corners with eight equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, edges with three equivalent Sr(3)As6 octahedra, and edges with four equivalent Sr(1)As6 octahedra. The corner-sharing octahedral tilt angles are 4°. In the third Sr site, Sr(3) is bonded to two equivalent As(2) and four equivalent As(1) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent Sr(2)As6 octahedra, corners with six equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(3)As6 octahedra, edges with three equivalent Sr(1)As6 octahedra, edges with three equivalent Sr(2)As6 octahedra, and edges with two equivalent Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 4-12°. Si(1) is bonded to one Si(1), one As(2), and two equivalent As(1) atoms to form distorted SiSiAs3 tetrahedra that share  a cornercorner with one As(2)Sr5Si octahedra, corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent As(1)Sr4Si2 octahedra, corners with three equivalent Sr(3)As6 octahedra, corners with four equivalent Sr(2)As6 octahedra,  an edgeedge with one Sr(1)As6 octahedra,  an edgeedge with one Sr(3)As6 octahedra, and  an edgeedge with one Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 19-82°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), and two equivalent Si(1) atoms to form distorted AsSr4Si2 octahedra that share corners with four equivalent As(1)Sr4Si2 octahedra, corners with four equivalent As(2)Sr5Si octahedra, corners with two equivalent Si(1)SiAs3 tetrahedra, edges with three equivalent As(1)Sr4Si2 octahedra, and edges with five equivalent As(2)Sr5Si octahedra. The corner-sharing octahedral tilt angles range from 4-95°. In the second As site, As(2) is bonded to one Sr(3), two equivalent Sr(1), two equivalent Sr(2), and one Si(1) atom to form AsSr5Si octahedra that share corners with three equivalent As(2)Sr5Si octahedra, corners with four equivalent As(1)Sr4Si2 octahedra,  a cornercorner with one Si(1)SiAs3 tetrahedra, edges with five equivalent As(1)Sr4Si2 octahedra, and edges with five equivalent As(2)Sr5Si octahedra. The corner-sharing octahedral tilt angles range from 1-90°.
Sr3(SiAs2)2 crystallizes in the monoclinic C2/c space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(2)As6 octahedra, corners with two equivalent Sr(3)As6 octahedra, corners with four equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(1)As6 octahedra, edges with three equivalent Sr(3)As6 octahedra, edges with four equivalent Sr(2)As6 octahedra, and edges with two equivalent Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 4-12°. Both Sr(1)-As(1) bond lengths are 3.19 Å. There are two shorter (3.14 Å) and two longer (3.18 Å) Sr(1)-As(2) bond lengths. In the second Sr site, Sr(2) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent Sr(3)As6 octahedra, corners with eight equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(2)As6 octahedra, edges with three equivalent Sr(3)As6 octahedra, and edges with four equivalent Sr(1)As6 octahedra. The corner-sharing octahedral tilt angles are 4°. Both Sr(2)-As(1) bond lengths are 3.34 Å. There are two shorter (3.16 Å) and two longer (3.17 Å) Sr(2)-As(2) bond lengths. In the third Sr site, Sr(3) is bonded to two equivalent As(2) and four equivalent As(1) atoms to form SrAs6 octahedra that share corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent Sr(2)As6 octahedra, corners with six equivalent Si(1)SiAs3 tetrahedra, edges with two equivalent Sr(3)As6 octahedra, edges with three equivalent Sr(1)As6 octahedra, edges with three equivalent Sr(2)As6 octahedra, and edges with two equivalent Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 4-12°. Both Sr(3)-As(2) bond lengths are 3.11 Å. There are two shorter (3.17 Å) and two longer (3.35 Å) Sr(3)-As(1) bond lengths. Si(1) is bonded to one Si(1), one As(2), and two equivalent As(1) atoms to form distorted SiSiAs3 tetrahedra that share  a cornercorner with one As(2)Sr5Si octahedra, corners with two equivalent Sr(1)As6 octahedra, corners with two equivalent As(1)Sr4Si2 octahedra, corners with three equivalent Sr(3)As6 octahedra, corners with four equivalent Sr(2)As6 octahedra,  an edgeedge with one Sr(1)As6 octahedra,  an edgeedge with one Sr(3)As6 octahedra, and  an edgeedge with one Si(1)SiAs3 tetrahedra. The corner-sharing octahedral tilt angles range from 19-82°. The Si(1)-Si(1) bond length is 2.36 Å. The Si(1)-As(2) bond length is 2.33 Å. Both Si(1)-As(1) bond lengths are 2.41 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), and two equivalent Si(1) atoms to form distorted AsSr4Si2 octahedra that share corners with four equivalent As(1)Sr4Si2 octahedra, corners with four equivalent As(2)Sr5Si octahedra, corners with two equivalent Si(1)SiAs3 tetrahedra, edges with three equivalent As(1)Sr4Si2 octahedra, and edges with five equivalent As(2)Sr5Si octahedra. The corner-sharing octahedral tilt angles range from 4-95°. In the second As site, As(2) is bonded to one Sr(3), two equivalent Sr(1), two equivalent Sr(2), and one Si(1) atom to form AsSr5Si octahedra that share corners with three equivalent As(2)Sr5Si octahedra, corners with four equivalent As(1)Sr4Si2 octahedra,  a cornercorner with one Si(1)SiAs3 tetrahedra, edges with five equivalent As(1)Sr4Si2 octahedra, and edges with five equivalent As(2)Sr5Si octahedra. The corner-sharing octahedral tilt angles range from 1-90°.