Synthesis, Crystal and Electronic Structure of the New Ternary Compound Ca3InAs3

Crystals of a new ternary compound in the Ca-In-As family, Ca3InAs3, have been successfully synthesized via flux growth techniques. This is only the third known compound between the respective elements. As elucidated by single-crystal X-ray diffraction measurements, Ca3InAs3 crystallizes in the orthorhombic space group Pnma (No. 62, Pearson symbol oP28) with unit cell parameters a = 12.296(2) angstrom, b = 4.2553(7) angstrom, and c = 13.735(2) angstrom. The smallest building motifs of the structure are InAs4 tetrahedra, which are connected to one another by shared As corners, forming infinite [InAs2As2/2] chains. The latter propagate along the crystallographic b-axis. The As-In-As bond angles within the InAs4 tetrahedra deviate from the ideal 109.5 degrees value and range from 98.12(2)degrees to 116.53(2)degrees, attesting to a small distortion from the regular tetrahedral geometry. Electronic structure calculations indicate the opening of a bandgap, consistent with the expected (Ca2+)(3)(In3+)(As3-)(3) formula breakdown based on conventional oxidation numbers. The calculations also show that the Ca-As interactions are an intermediate between covalent and ionic, while providing evidence of strong covalent features of the In-As interactions. Weak s-p hybridization of In states was observed, supporting the experimentally found deviation of the InAs4 moiety from the ideal tetrahedral symmetry.

Automated summary

Crystals of a new ternary compound, Ca3InAs3, have been successfully synthesized in the Ca-In-As family. The compound crystallizes in the orthorhombic space group and has InAs4 tetrahedra as the smallest building motifs. Electronic structure calculations confirm the opening of a bandgap and show intermediate covalent/ionic interactions between Ca and As, as well as strong covalent features of the In-As interactions.