LAUSR

Abstract Recently, the orthorhombic structures of Na3MO4 (M=Np and Pu) have been successfully synthesized by Smith et al. In this paper, the physical characteristics namely lattice parameters, elastic constants Cij, polycrystalline moduli, anisotropic properties, Vicker's hardness Hv and Debye temperature of them have been systematically predicted for the first time by employing the first-principles calculations. The predicted Cij reveal that the Na3NpO4 and Na3PuO4 are mechanically stable. The obtained polycrystalline moduli indicated that both of Na3MO4 behaves the brittle behavior with the Hv is less than 10.0 GPa. Furthermore, the anisotropy properties of Na3MO4 are further illustrated by using three different kinds of anisotropy factors and direction-dependent of the bulk moduli B, shear moduli G and Young's moduli E. Finally, the averaged sound velocity vm and Debye temperature θD are investigated and analyzed.