The methodology was developed in earlier work (cf. and the papers cited therein). Essentially, the search for the ground state structures with minimal energies was performed with unconstrained geometry optimizations within the DFT-based plane-wave Vienna Ab initio Simulation Package (VASP) using the projector augmented wave (PAW) method for potentials . Within the DFT, the effects of exchange and correlation (XC) were treated using Generalized Gradient Approximation (GGA) scheme . Investigation of the mechanical properties was based on the calculations of the elastic properties by performing finite distortions of the lattice and deriving the elastic constants from the strain-stress relationship. The calculated elastic constants C ij were then used to obtain the bulk (B) and the shear (G) moduli using the Voigt averaging method based on uniform strain. Besides the mechanical properties, the dynamic stability was determined from the calculations of the phonons and illustrated with the corresponding band structures in the reciprocal space (Brillouin zone) using the "Phonopy" interface code based on the Python language . The structures were plotted using the VESTA graphical program . For the evaluation of the electronic properties, the band structures were obtained with the all-electrons augmented spherical wave method ASW .