KPt2Se3 is Ilmenite-like structured and crystallizes in the trigonal R-3m space group. K(1) is bonded in a 6-coordinate geometry to three equivalent Pt(2) and three equivalent Se(1) atoms. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to six equivalent Se(1) atoms to form edge-sharing PtSe6 octahedra. In the second Pt site, Pt(2) is bonded to two equivalent K(1) and four equivalent Se(1) atoms to form PtK2Se4 octahedra that share corners with six equivalent Se(1)KPt3 trigonal pyramids, edges with two equivalent Pt(1)Se6 octahedra, and edges with four equivalent Pt(2)K2Se4 octahedra. Se(1) is bonded to one K(1), one Pt(1), and two equivalent Pt(2) atoms to form distorted SeKPt3 trigonal pyramids that share corners with three equivalent Pt(2)K2Se4 octahedra, corners with five equivalent Se(1)KPt3 trigonal pyramids, and edges with four equivalent Se(1)KPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 37-79°.
KPt2Se3 is Ilmenite-like structured and crystallizes in the trigonal R-3m space group. K(1) is bonded in a 6-coordinate geometry to three equivalent Pt(2) and three equivalent Se(1) atoms. All K(1)-Pt(2) bond lengths are 3.36 Å. All K(1)-Se(1) bond lengths are 3.45 Å. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to six equivalent Se(1) atoms to form edge-sharing PtSe6 octahedra. All Pt(1)-Se(1) bond lengths are 2.52 Å. In the second Pt site, Pt(2) is bonded to two equivalent K(1) and four equivalent Se(1) atoms to form PtK2Se4 octahedra that share corners with six equivalent Se(1)KPt3 trigonal pyramids, edges with two equivalent Pt(1)Se6 octahedra, and edges with four equivalent Pt(2)K2Se4 octahedra. All Pt(2)-Se(1) bond lengths are 2.46 Å. Se(1) is bonded to one K(1), one Pt(1), and two equivalent Pt(2) atoms to form distorted SeKPt3 trigonal pyramids that share corners with three equivalent Pt(2)K2Se4 octahedra, corners with five equivalent Se(1)KPt3 trigonal pyramids, and edges with four equivalent Se(1)KPt3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 37-79°.