PdZn or ZnPd: Charge Transfer and Pd–Pd Bonding as the Driving Force for the Tetragonal Distortion of the Cubic Crystal Structure

The intermetallic compound PdZn was reported to have two modifications, the tetragonal CuAu‐type low‐temperature phase and the cubic CsCl‐type high‐temperature phase. The existence of the cubic high‐temperature phase at the equiatomic composition could not be proven experimentally. Calculations of the total energy reveal a minimum at c/a = 1.155, clearly excluding the cubic structure at the equiatomic composition in the system Pd‐Zn. Analysis of the chemical bonding applying the electron localizability approach reveals charge transfer from zinc to palladium and proves direct Pd–Pd interactions in the (001) plane to be the main reason for the tetragonal distortion of the cubic CsCl‐type structural pattern for ZnPd.