CaPt4P6, first calcium-containing representative of the ternary pyrite-derived pnictides of the BaPt4As6 type: Synthesis, crystal, and electronic structure

Mixed calcium-platinum phosphide CaPt4P6 was synthesized using flux-assisted high-temperature ampoule technique. According to single-crystal XRD data it crystallizes in the monoclinic space group C2/c with Z ​= ​4 (a ​= ​8.1361(3) Å, b ​= ​7.9489(3) Å, c ​= ​11.3803(5) Å, β ​= ​90.860(2)o, R1 ​= ​0.0240, wR2 ​= ​0.0618) and belongs to the BaPt4As6 structure type, the structure of which is derived from pyrite structure where one atom of alkaline earth metal per formula unit occupies P2-unit position. DFT calculations predict all known representatives of the BaPt4As6 structure type to be narrow-gap semiconductors (calculated bandgap values are: 0.43 ​eV (CaPt4P6), 0.57 ​eV (SrPt4P6), 0.27 ​eV (SrPt4As6) and 0.40 ​eV (BaPt4As6)). Bonding analysis establishes that all these compounds are based on the 3D framework of the Pt-Pn and Pn-Pn interactions, with AE cations occupying the voids with varying degree of the distortion of the AE coordination. [Display omitted] •Calcium-platinum phosphide, CaPt4P6, was synthesized from lead flux.•It was characterized by EDX and single-crystal XRD.•It is the first Ca-containing compound of the BaPt4As6-type.•According to the DFT calculations, it is a narrow-gap semiconductor.