Stability of 2D Alkaline-Earth Metal Silicides, Germanides and Stannides

By means of ab initio calculations, we have estimated stability of 2D Me[Formula: see text] ([Formula: see text], Ca, Sr, Ba and [Formula: see text], Ge, Sn) in the T and Td phases, which are similar to the ones of 2D transition metal chalcogenides, in addition to their phonon spectra. The T phase is found to be more stable for 2D Ca[Formula: see text], Sr[Formula: see text] and Ba[Formula: see text], whereas the Td phase is predicted to be the ground state for 2D Mg[Formula: see text]. We have also discussed that imaginary frequencies in the calculated phonon spectra of 2D Me[Formula: see text], which appeared in the vicinity of the [Formula: see text] point, were not necessarily associated with the dynamic instability.