Lawrence Berkeley National Laboratory

Pt(Cu0.67Sn0.33) has recently been found in a natural sample. In order to be able to characterize this new ternary compound, we synthesized it from the elements. Samples were characterized by X-ray powder diffraction, differential scanning calorimetry, thermal relaxation calorimetry, and scanning electron microscopy studies. Density functional theory-based model calculations complemented the experimental studies. Pt(Cu0.67Sn0.33) was already formed at a relatively low temperature of 773 K. Rietveld refinement of Pt(Cu0.67Sn0.33) has been carried out in CuAu-type or L10-type structure, space group P4∕mmm, with Pt on 0,0,0 and disordered Cu and Sn on [Formula presented], [Formula presented], [Formula presented] and Z = 1. The lattice parameters are a = 2.823(1) Å, c = 3.64(1) Å, and V = 29.00(4) Å 3; which are in good agreement with values obtained earlier on the natural sample and with the results of DFT calculations. The vibrational entropy for Pt(Cu0.67Sn0.33) is S298.15vib = 79.9(7) J mol−1 K−1. The pressure dependence up to 36(2) GPa of the unit-cell volume and the lattice parameters and unit-cell volume have been obtained by synchrotron based powder diffraction using a diamond anvil cell. A fit of a 3rd-order Birch–Murnaghan equation of state to the Pt(Cu0.67Sn0.33) (p,V)-data results in a bulk modulus of B0 = 215(27) GPa and B′ = 5(2).