Pd2Cd11−δ (0.21≤δ≤0.51)–a partly disordered γ-brass type phase and Pd0.238Cd0.762-a γ-brass related incommensurate phase in the palladium–cadmium system

The Cd rich part of the Cd–Pd phase diagram was reassessed by means of synthesis and single crystal and powder X-ray diffraction. The region contains two phases that have been reported to have substantial compositional widths, Cd11Pd2 and Cd4Pd. The phase Cd11Pd2 that has previously been reported to be a disordered γ-brass crystallizing is space group P4̄3m is here shown to crystallize in I4̄3m and the mechanism for compositional variation is explained. The phase Pd4Cd has previously been shown to constitute a phase field or a phase bundle of modulated structures and here we determine the structure of a compound Pd0.238Cd0.762 which crystallizes in the orthorhombic superspace group Fmmm(α00)0s0 (F=[(½, ½, 0, 0); (½, 0, ½, 0 ); (0, ½, ½, 0 )] with the fundamental cell dimensions a=4.687(2) Å, b=10.000(1) Å, c=14.140(2) Å, q=0.6432(6)a⁎.

The crystal structures of the partly disordered γ-brass type Pd2Cd11−δ (0.21≤δ≤0.51) and γ-brass related Pd0.238Cd0.762 in the palladium–cadmium binary system.Figure optionsDownload as PowerPoint slideHighlights
► Partly disordered γ-brass type Pd2Cd11−δ (0.21≤δ≤0.51) and γ-brass related Pd0.238Cd0.762 have been synthesized.
► The Pd2Cd11−δ structure have been described by cluster concept.
► Incommensurately modulated Pd0.238Cd0.762 have been described by (3+1) D space description.
► The structure of Pd0.238Cd0.762 has two different chains of atomic subunits, each with their own translational periodicities.