|Title||Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae = Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||Samal, SL, Gulo, F, Corbett, JD|
|Type of Article||Article|
|Keywords||approximant, au-ga system, crystal-structure, examples, frameworks, gallium, gold substitution, intermetallic phases, networks, tunnels|
Three new ternary polar intermetallic cornpounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae-Pt-Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) angstrom) contains a 3D array of separate Cd-8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd-8[Pt(1)](6/2)[Pt(2)](4/8). The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca-6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt(2)Cd(4), Ae = Sr, Ba, are tetragonal (P4(2)/mnm, Z = 2, a approximate to 8.30 angstrom, c approximate to 4.47 angstrom) and contain chains of edge-sharing Cd-4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt-Cd and Pd-Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt-8, and Pd-16, and that some terms remain incomparable, Ca-Cd versus Er-Pd.
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