Electronic Structure of Platinum-Group Minerals: Prediction of Semiconductor Band Gaps

Abstract We report first-principle electronic structure calculations of the three representative minerals of the platinum group: cooperite (PtS), braggite (PdPt3S4) and sperrylite (PtAs2) using the Tight-Binding Linear Muffin Tin Orbital (TB-LMTO) technique. We predict non-metallic behaviour for all three minerals with semiconductor band gaps of 1.31, 0.89 and 0.34eV, respectively. In particular, our calculation is in excellent agreement with the experimental value of 1.4eV deduced from diffuse-reflectance measurement for cooperite. We argue that the strong bonding between the Pt 5d and S(As) 3p(4p) states plays a crucial role in the formation of the semi-conductor band gap. Key Words: Platinum group mineralselectronic structureband gaps