Ab initio calculation of the stability of one-dimensional long-period structures in the Cu3Pd compound

The relative stabilities of L1(2), D0(22), D0(23) and several one-dimensional (1D) long period structures (LPSs) in the Cu3Pd intermetallic compound are investigated employing the Vienna ab initio simulation package. The energy effects due to the tetragonal distortion of the D0(22) and D0(23) structures and other 1D LPSs are small, and those due to the cell internal displacements of the atoms in the LPSs are negligible. With distortion, the [3] structure is found to be the ground state; however, the structures [4] and [43] are rather close in energy to this ground state. The energy results are discussed in the framework of the axial next-nearest-neighbour Ising model. Predictions of the energy differences between series of 1D LPSs and the L1(2) structure are provided. The (001) antiphase boundary energy is also determined using the same model.