Phase stability, elastic, anisotropic properties, lattice dynamical and thermodynamic properties of B12M (M=Th, U, Np, Pu) dodecaborides

Dodecaborides are promising high strength ceramic and refractory materials, due to the excellent physical properties. However, the scarce systematic investigations of physical properties of B12M (M=Th, U, Np, Pu) dodecaborides hinder the better applications of these dodecaborides. By means of the first-principles approach, we systemically investigated the phase stability, elastic, anisotropic properties, dynamical stability and thermodynamic properties of B12M (M=Th, U, Np, Pu) dodecaborides. The optimized structure constants are consistent with available experimental data. The values of formation enthalpies and V/V0 under pressure indicate B12M have good phase stability. The elastic parameters and modulus indicate that B12M dodecaborides are all brittle and superhard materials. The results of anisotropic factors, 3D surface contours and 2D projections of B12M indicate that they are all anisotropic, but the extent of anisotropy is relatively small. Anisotropy of acoustic velocities and the 2D planar projections of the minimum thermal conductivity are also calculated and discussed. The lattice dynamic properties indicate that four dodecaborides are all satisfied with the dynamic stability conditions. The relationship between thermodynamic quantity and temperature was calculated and discussed for four dodecaborides.