Na3Eu2(SiTe3)2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form NaTe6 octahedra that share corners with four equivalent Eu(1)Te6 octahedra, corners with two equivalent Si(1)SiTe3 tetrahedra, edges with three equivalent Na(1)Te6 octahedra, edges with three equivalent Na(2)Te6 octahedra, edges with four equivalent Eu(1)Te6 octahedra, and edges with two equivalent Si(1)SiTe3 tetrahedra. The corner-sharing octahedral tilt angles are 5°. In the second Na site, Na(2) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form NaTe6 octahedra that share corners with four equivalent Eu(1)Te6 octahedra, corners with two equivalent Si(1)SiTe3 tetrahedra, edges with four equivalent Eu(1)Te6 octahedra, edges with six equivalent Na(1)Te6 octahedra, and edges with two equivalent Si(1)SiTe3 tetrahedra. The corner-sharing octahedral tilt angles are 5°. Eu(1) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form EuTe6 octahedra that share corners with two equivalent Na(2)Te6 octahedra, corners with four equivalent Na(1)Te6 octahedra, corners with six equivalent Si(1)SiTe3 tetrahedra, edges with two equivalent Na(2)Te6 octahedra, edges with three equivalent Eu(1)Te6 octahedra, and edges with four equivalent Na(1)Te6 octahedra. The corner-sharing octahedral tilt angles are 5°. Si(1) is bonded to one Si(1), one Te(2), and two equivalent Te(1) atoms to form SiSiTe3 tetrahedra that share  a cornercorner with one Na(2)Te6 octahedra,  a cornercorner with one Te(2)Na3Eu2Si octahedra, corners with two equivalent Na(1)Te6 octahedra, corners with two equivalent Te(1)Na3Eu2Si octahedra, corners with six equivalent Eu(1)Te6 octahedra,  an edgeedge with one Na(2)Te6 octahedra, and edges with two equivalent Na(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 20-77°. There are two inequivalent Te sites. In the first Te site, Te(1) is bonded to one Na(2), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom to form TeNa3Eu2Si octahedra that share corners with three equivalent Te(2)Na3Eu2Si octahedra, corners with four equivalent Te(1)Na3Eu2Si octahedra,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with four equivalent Te(2)Na3Eu2Si octahedra, and edges with six equivalent Te(1)Na3Eu2Si octahedra. The corner-sharing octahedral tilt angles range from 0-91°. In the second Te site, Te(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom to form TeNa3Eu2Si octahedra that share  a cornercorner with one Te(2)Na3Eu2Si octahedra, corners with six equivalent Te(1)Na3Eu2Si octahedra,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na3Eu2Si octahedra, and edges with eight equivalent Te(1)Na3Eu2Si octahedra. The corner-sharing octahedral tilt angles range from 0-91°.
Na3Eu2(SiTe3)2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form NaTe6 octahedra that share corners with four equivalent Eu(1)Te6 octahedra, corners with two equivalent Si(1)SiTe3 tetrahedra, edges with three equivalent Na(1)Te6 octahedra, edges with three equivalent Na(2)Te6 octahedra, edges with four equivalent Eu(1)Te6 octahedra, and edges with two equivalent Si(1)SiTe3 tetrahedra. The corner-sharing octahedral tilt angles are 5°. Both Na(1)-Te(2) bond lengths are 3.30 Å. There are two shorter (3.27 Å) and two longer (3.40 Å) Na(1)-Te(1) bond lengths. In the second Na site, Na(2) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form NaTe6 octahedra that share corners with four equivalent Eu(1)Te6 octahedra, corners with two equivalent Si(1)SiTe3 tetrahedra, edges with four equivalent Eu(1)Te6 octahedra, edges with six equivalent Na(1)Te6 octahedra, and edges with two equivalent Si(1)SiTe3 tetrahedra. The corner-sharing octahedral tilt angles are 5°. Both Na(2)-Te(2) bond lengths are 3.42 Å. All Na(2)-Te(1) bond lengths are 3.28 Å. Eu(1) is bonded to two equivalent Te(2) and four equivalent Te(1) atoms to form EuTe6 octahedra that share corners with two equivalent Na(2)Te6 octahedra, corners with four equivalent Na(1)Te6 octahedra, corners with six equivalent Si(1)SiTe3 tetrahedra, edges with two equivalent Na(2)Te6 octahedra, edges with three equivalent Eu(1)Te6 octahedra, and edges with four equivalent Na(1)Te6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Eu(1)-Te(2) bond lengths are 3.30 Å. All Eu(1)-Te(1) bond lengths are 3.31 Å. Si(1) is bonded to one Si(1), one Te(2), and two equivalent Te(1) atoms to form SiSiTe3 tetrahedra that share  a cornercorner with one Na(2)Te6 octahedra,  a cornercorner with one Te(2)Na3Eu2Si octahedra, corners with two equivalent Na(1)Te6 octahedra, corners with two equivalent Te(1)Na3Eu2Si octahedra, corners with six equivalent Eu(1)Te6 octahedra,  an edgeedge with one Na(2)Te6 octahedra, and edges with two equivalent Na(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 20-77°. The Si(1)-Si(1) bond length is 2.38 Å. The Si(1)-Te(2) bond length is 2.59 Å. Both Si(1)-Te(1) bond lengths are 2.60 Å. There are two inequivalent Te sites. In the first Te site, Te(1) is bonded to one Na(2), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom to form TeNa3Eu2Si octahedra that share corners with three equivalent Te(2)Na3Eu2Si octahedra, corners with four equivalent Te(1)Na3Eu2Si octahedra,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with four equivalent Te(2)Na3Eu2Si octahedra, and edges with six equivalent Te(1)Na3Eu2Si octahedra. The corner-sharing octahedral tilt angles range from 0-91°. In the second Te site, Te(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom to form TeNa3Eu2Si octahedra that share  a cornercorner with one Te(2)Na3Eu2Si octahedra, corners with six equivalent Te(1)Na3Eu2Si octahedra,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na3Eu2Si octahedra, and edges with eight equivalent Te(1)Na3Eu2Si octahedra. The corner-sharing octahedral tilt angles range from 0-91°.