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

By means of ab initio calculations, we have estimated stability of 2D Me 2 X (Me = Mg , Ca, Sr, Ba and X = Si , 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 2 X , Sr 2 X and Ba 2 X , whereas the Td phase is predicted to be the ground state for 2D Mg 2 X. We have also discussed that imaginary frequencies in the calculated phonon spectra of 2D Me 2 X , which appeared in the vicinity of the Γ point, were not necessarily associated with the dynamic instability. [ABSTRACT FROM AUTHOR]