Role of NiAs phase in pressure-induced structural phase transitions in IIA-VI chalcogenides

The plane-wave-based pseudopotential method within density-functional theory has been used to study ambient- and high-pressure phases of a series of IIA-VI semiconductors. We analyze the stability of sodium chloride (NaCl), wurtzite, zinc blende, nickel arsenide (NiAs), and cesium chloride structures: in these compounds. Static structural properties as well as energetics are reported. The intrinsic bulk stability of NaCl and its hexagonal analog, NiAs phases, has been addressed here. The static structural properties as well as the total energies as a function of Volume for these two phases are found to be close to each other compared to other structures. We observe that with increasing ionicity of the compounds, the stability of the NaCl phase increases over the NiAs phase. From our calculations, a maximum total energy difference of similar to 15 mRy per molecule at equilibrium volume of these phases is observed in the IIA-VI chalcogenides.