Verifying predictions of the L13 crystal structure in Cd-Pt and Pd-Pt by exhaustive enumeration

In 2001, S. Müller and A. Zunger Phys. Rev. Lett. 87, 165502 2001 predicted a never-before-observed crystal structure in Ag-Pd. Recently, Curtarolo predicted the same structure to be stable in Pt-Cd and Pt-Pd S. Curtarolo et al., CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 29, 163 2005 . The predicted structure is unique in several ways. Though never seen in any other face-centered-cubic-based intermetallic binary compound or ordered alloy, it is relatively simple—it contains only four atoms per unit cell. Furthermore, the structure is the only one of this small size, except the L12 structure, that cannot be characterized as a simple stacking of layers where each layer contains only one kind of atom. We construct a first-principlesbased Hamiltonian and search it for the thermodynamically stable lowest energy structures. Using a practically exhaustive enumeration of about three million of the most likely candidate structures, we find that this new structure, designated L13, is indeed a ground state in both Cd-Pt and Pd-Pt. Experimental efforts to validate the predictions are underway.