Structural and Theoretical Investigations on the Unique Coloring Scheme of the γ-Brass Type Phase: Cu5+δCd8-δ (-1.0≤δ≤0.1)

The crystal structure of the gamma-brass type Cu5+delta Cd8-delta (-1.0 <=delta <= 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 I4?3m (217). Mixing of Cu with Cd leads to a significant phase width. At the limiting composition, a previously unreported ordered compound Cu4Cd9 is formed. The structure of all compounds is described by a 26-atom gamma-cluster. Electronic structure calculations on the model structure built according to the ordered Cu4Cd9, show the presence of a pseudo-gap at the Fermi level in the electronic density of states, which is consistent with other gamma-brass type phases. However, the site preference of Cu and Cd atoms is different from the other reported gamma-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 Cu4Cd9 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.

Automated summary

The crystal structure of the Cu5+δCd8-δ compound in the Cu-Cd binary system has been analyzed using X-ray diffraction techniques. The compounds exhibit a cubic space group and Cu4Cd9 is formed at the limiting composition. The structure of all compounds can be described by a 26-atom gamma-cluster. Electronic structure calculations show the presence of a pseudo-gap at the Fermi level in the Cu4Cd9 structure.