The structures of the binary compounds have all been subjected to geometry relaxations of the atomic positions and lattice constants down to the respective ground states characterized by minimum energies. The protocol consists of iterative calculations performed using the DFT-based plane-wave Vienna Ab initio Simulation Package (VASP) . For the atomic potentials, the projector augmented wave (PAW) method was used . The exchange and correlation effects were treated within a Generalized Gradient Approximation (GGA) scheme . The relaxation of the atoms to the ground state geometry was done by applying a conjugate-gradient algorithm . A tetrahedron method with corrections according to the Methfessel-Paxton scheme was used for geometry optimization and energy calculations, respectively. A special k-point sampling was applied to approximate the reciprocal space Brillouin zone (BZ) integrals. For better reliability, the optimization of the structural parameters was carried out along with successive self-consistent cycles with increasing k-mesh until the forces on atoms were less than 0.02 eV/Å and the stress components were below 0.003 eV/Å 3 . The plane waves energy cutoff was 400 eV.