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 Ca-10(Pt4As8)(Fe2As2)(5) (T-C approximate to 25 K). The Ca-10(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 Ca-10(Pt4As8)(Fe2As2)(5) may be described as a mixture of anisotropic contributions of covalent, ionic, and metallic interatomic and inter-block interactions.