Ab initio study of the nature of the chemical bond and electronic structure of the layered phase Ca10(Pt4As8)(Fe2As2)5 as a parent system in the search for new superconducting iron-containing materials

Ab initio calculations were used in a detailed study of chemical bonding and electronic structure of the recently discovered superconducting tetragonal phase Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ (T_C 25 K). The Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ phase is metal-like, mainly due to the Fe3d states of the (Fe₂As₂)₅ blocks. The electronic spectrum of the (Pt₄As₈) blocks is similar to a semi-metal with very low density of states at the Fermi level. Chemical bonding in Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ may be described as a mixture of anisotropic contributions of covalent, ionic, and metallic interatomic and inter-block interactions.