Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN2 and PtN2

This paper studies the elastic and electronic structure propertiesof two new low-energy structures of PdN₂ and PtN₂ byfirst-principles calculations. It finds that tetragonal andmonoclinic structures are more stable than a pyrite one.The always positive eigenvalues of the elastic constant matrixconfirm that both the tetragonal and monoclinic structures areelastically stable. The origin of the low bulk modulus of the twostructures is discussed. The results of the calculated densityof states show that both of the two low-energy structures aremetallic.