The structural, mechanical and electronic properties of Ba_xN_y compounds

The effects of pressure on structures, enthalpies, elastic properties, mechanical stability and electronic properties of BaN₂, Ba₂N, BaN₆ and BaN₅ have been investigated using first-principles calculations. Based on the experimental and theoretical parameters, the crystal structures of four Ba–N compounds at zero pressure and high pressure have been built and studied. The enthalpies of BaN₂, Ba₂N, BaN₆ and BaN₅ decrease gradually within the range of 0 GPa–100 GPa. The mechanical stability of compounds in the pressure range from 0 GPa to 100 GPa has been estimated by the modified Born stability conditions under pressure. Through the study of elastic modulus, it is found that the increasing pressure can enhance the ability of resisting elastic deformation. The B/G and Poisson's ratio shows that BaN₂, BaN₆ as well as BaN₅ are ductile, and the brittle-tough transition was observed for Ba₂N. The band structures and density of states are studied in order to explore the characteristics of the motion of electrons in barium nitrides.