NaPt2Se3 is Ilmenite-like structured and crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to three equivalent Pt(1) and three equivalent Se(1) atoms. In the second Na site, Na(2) is bonded to three equivalent Pt(1) and three equivalent Se(2) atoms to form distorted NaPt3Se3 pentagonal pyramids that share corners with three equivalent Pt(2)Se6 octahedra, corners with six equivalent Se(1)NaPt3 trigonal pyramids, edges with three equivalent Pt(1)Na2Se4 octahedra, and edges with three equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles are 21°. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to one Na(1), one Na(2), two equivalent Se(1), and two equivalent Se(2) atoms to form PtNa2Se4 octahedra that share corners with three equivalent Se(1)NaPt3 trigonal pyramids, corners with three equivalent Se(2)NaPt3 trigonal pyramids, edges with two equivalent Pt(2)Se6 octahedra, edges with four equivalent Pt(1)Na2Se4 octahedra, and  an edgeedge with one Na(2)Pt3Se3 pentagonal pyramid. In the second Pt site, Pt(2) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form PtSe6 octahedra that share corners with three equivalent Na(2)Pt3Se3 pentagonal pyramids and edges with six equivalent Pt(1)Na2Se4 octahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Pt(2), and two equivalent Pt(1) atoms to form SeNaPt3 trigonal pyramids that share corners with three equivalent Pt(1)Na2Se4 octahedra, corners with two equivalent Na(2)Pt3Se3 pentagonal pyramids, corners with two equivalent Se(1)NaPt3 trigonal pyramids, corners with three equivalent Se(2)NaPt3 trigonal pyramids, edges with two equivalent Se(1)NaPt3 trigonal pyramids, and edges with two equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 1-73°. In the second Se site, Se(2) is bonded to one Na(2), one Pt(2), and two equivalent Pt(1) atoms to form SeNaPt3 trigonal pyramids that share corners with three equivalent Pt(1)Na2Se4 octahedra, corners with two equivalent Se(2)NaPt3 trigonal pyramids, corners with three equivalent Se(1)NaPt3 trigonal pyramids,  an edgeedge with one Na(2)Pt3Se3 pentagonal pyramid, edges with two equivalent Se(1)NaPt3 trigonal pyramids, and edges with two equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 40-86°.
NaPt2Se3 is Ilmenite-like structured and crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to three equivalent Pt(1) and three equivalent Se(1) atoms. All Na(1)-Pt(1) bond lengths are 3.08 Å. All Na(1)-Se(1) bond lengths are 3.18 Å. In the second Na site, Na(2) is bonded to three equivalent Pt(1) and three equivalent Se(2) atoms to form distorted NaPt3Se3 pentagonal pyramids that share corners with three equivalent Pt(2)Se6 octahedra, corners with six equivalent Se(1)NaPt3 trigonal pyramids, edges with three equivalent Pt(1)Na2Se4 octahedra, and edges with three equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles are 21°. All Na(2)-Pt(1) bond lengths are 3.02 Å. All Na(2)-Se(2) bond lengths are 3.12 Å. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to one Na(1), one Na(2), two equivalent Se(1), and two equivalent Se(2) atoms to form PtNa2Se4 octahedra that share corners with three equivalent Se(1)NaPt3 trigonal pyramids, corners with three equivalent Se(2)NaPt3 trigonal pyramids, edges with two equivalent Pt(2)Se6 octahedra, edges with four equivalent Pt(1)Na2Se4 octahedra, and  an edgeedge with one Na(2)Pt3Se3 pentagonal pyramid. Both Pt(1)-Se(1) bond lengths are 2.46 Å. Both Pt(1)-Se(2) bond lengths are 2.46 Å. In the second Pt site, Pt(2) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form PtSe6 octahedra that share corners with three equivalent Na(2)Pt3Se3 pentagonal pyramids and edges with six equivalent Pt(1)Na2Se4 octahedra. All Pt(2)-Se(1) bond lengths are 2.52 Å. All Pt(2)-Se(2) bond lengths are 2.53 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Pt(2), and two equivalent Pt(1) atoms to form SeNaPt3 trigonal pyramids that share corners with three equivalent Pt(1)Na2Se4 octahedra, corners with two equivalent Na(2)Pt3Se3 pentagonal pyramids, corners with two equivalent Se(1)NaPt3 trigonal pyramids, corners with three equivalent Se(2)NaPt3 trigonal pyramids, edges with two equivalent Se(1)NaPt3 trigonal pyramids, and edges with two equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 1-73°. In the second Se site, Se(2) is bonded to one Na(2), one Pt(2), and two equivalent Pt(1) atoms to form SeNaPt3 trigonal pyramids that share corners with three equivalent Pt(1)Na2Se4 octahedra, corners with two equivalent Se(2)NaPt3 trigonal pyramids, corners with three equivalent Se(1)NaPt3 trigonal pyramids,  an edgeedge with one Na(2)Pt3Se3 pentagonal pyramid, edges with two equivalent Se(1)NaPt3 trigonal pyramids, and edges with two equivalent Se(2)NaPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 40-86°.