Structural and theoretical investigations on the unique coloring scheme of the γ-brass type phase. Cu${}_{5+\delta }$Cd${}_{8-\delta }$ (-1.0≤δ≤0.1)

The crystal structure of the γ-brass type Cu${}_{5+\delta }$Cd${}_{8-\delta }$ (-1.0≤δ≤0.1) in the Cu-Cd binary system has been analyzed by powder and single crystal X-ray diffraction. All the compounds crystallize in the cubic space group I$\overline{4}$3m (217). Mixing of Cu with Cd leads to a significant phase width. At the limiting composition, a previously unreported ordered compound Cu${}_4$Cd${}_9$ is formed. The structure of all compounds is described by a 26-atom γ-cluster. Electronic structure calculations on the model structure built according to the ordered "Cu${}_4$Cd${}_9$", show the presence of a pseudo-gap at the Fermi level in the electronic density of states, which is consistent with other γ-brass type phases. However, the site preference of Cu and Cd atoms is different from the other reported γ-brass type structures in the Zn- and Cd-rich phases. To address the "coloring problem", a series of model structures were constructed with the composition Cu${}_4$Cd${}_9$ and their total energies were compared with first-principle calculations using ABINIT code. LOBSTER package was implemented to extract the bonding information by crystal orbital Hamilton population calculations. (© 2022 Wiley‐VCH GmbH)