Pt-rich intermetallic APt8P2 (A = Ca and La)

The combination of experimental and theoretical investigation of two new Pt-rich intermetallic compounds: APt8P2 (A = Ca and La) is presented, including solid-state synthesis, crystal structure determination, physical properties characterization and chemical bonding analysis. APt8P2 was obtained through the high-temperature pellet synthesis. According to both single crystal and powder X-ray diffraction results, APt8P2 crystallize in the monoclinic DyPt8P2-type structure with space group I2/m (S.G. 12). Crystal structure of APt8P2 can be considered as intercalating multiple Pt layers into APt2P2. Magnetic susceptibility measurement indicates diamagnetism of both compounds. The specific heat down to 1.8 K shows no evidence for bulk superconductivity in either CaPt8P2 and LaPt8P2. Electronic structure calculations match well with the observed structural stability and metallic behavior. The following Crystal Orbital Hamiltonian Population (-COHP) calculations suggest that the difference of Pt-Pt antibonding interaction could be the key factor that results in the shrinkage of c axis in APt8P2.