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The binary Ru4Si3 remained the only compound in its structure type for more than 60 years. Herein, we report the synthesis and crystal structure of the first ternary silicide (Ir4−xCuSi2) in the Ru4Si3-type structure, which can be derived from RuSi by unit cell twinning. According to single-crystal X-ray diffraction, Ir vacancies exist along the twin boundary. Ir4−xCuSi2 exhibits a distorted structure compared to Ru4Si3, as the larger Cu selectively replaces Si on only one of three possible sites, leading to zigzag chains with short Cu–Cu distances. Furthermore, DFT calculations show that the rigid band approximation does not apply to this structure type, but the similarities of electronic structures of the ideal binary and ternary compositions suggest that this structure type can accommodate a large variety of elemental substitutions without a significant change of its electronic structure if a similar valence electron count is maintained, hinting at a potentially rich substitutional chemistry. [ABSTRACT FROM AUTHOR]

A new ternary phase, TiIrB, was synthesized by arc-melting of the elements and characterized by powder X-ray diffraction. The compound crystallizes in the orthorhombic Ti1+xRh2−x+yIr3−yB3 structure type, space group Pbam (no. 55) with the lattice parameters a = 8.655(2), b = 15.020(2), and c = 3.2271(4) Å. Density Functional Theory (DFT) calculations were carried out to understand the electronic structure, including a Bader charge analysis. The charge distribution of TiIrB in the Ti1+xRh2−x+yIr3−yB3-type phase has been evaluated for the first time, and the results indicate that more electron density is transferred to the boron atoms in the zigzag B4 units than to isolated boron atoms. [ABSTRACT FROM AUTHOR]