The crystal structures of m,o-Ce3Pt4Sn6 and Ce1−xPt6Al13+2x

Abstract The crystal structures of two novel ternary compounds, Ce 3 Pt 4 Sn 6 and Ce 1−x Pt 6 Al 13+2x (x = 0.207), have been derived by direct methods from X-ray single crystal data. Whereas Ce 1−x Pt 6 Al 13+2x is of a new structure type ( a  = 1.42224(2) nm, c  = 0.87367(1) nm, space group P 6 ¯ 2 m ), Ce 3 Pt 4 Sn 6 was found to crystallize in two different crystal modifications, (i) a monoclinic variant ( a  = 0.93682(2) nm, b  = 0.46145(1) nm, c  = 1.40434(3) nm, β  = 99.635(1)°, space group P 2 1 / m ), which is isotypic with the Y 3 Pt 4 Ge 6 -type and (ii) an orthorhombic modification ( a  = 2.76394(4) nm, b  = 0.460588(7) nm, c  = 0.93530(1) nm, space group Pnma ), which crystallizes with the ordered Pr 3 Pt 4 Ge 6 -type. For the monoclinic arrangement m-Ce 3 Pt 4 Sn 6 an intrinsically defect growth pattern was found – it grows in two related motifs (opposite directions of pentagonal units) in the ratio of 90% : 10% ensuring a stoichiometric composition. TEM observation directly revealed intrinsic building defects detected by single crystal X-ray diffraction for m-Ce 3 Pt 4 Sn 6 . Diffuse streaks in electron diffraction and inhomogeneous contrasts in a high resolution TEM image indicate the existence of a random stacking sequence between two related motifs.