We study the structures and magnetic phase stability of rare earth diboride compounds, RB2, using density functional simulations within the local density approximation. At zero pressure the hexagonal (P6/mmm) structure is energetically stable and at high pressure these materials prefer to keep the same structure. The five different elastic constants, bulk modulus, shear modulus, and hardness of all the hexagonal compounds have been calculated. The pressure dependence of the volumes is determined. The calculated large bulk modulus and high hardness reveal that they are incompressible and hard materials. The structural parameters and magnetic phase stability for RB2 (R = Tb, Dy, Ho, Er, Tm, and Yb) compare quite well with experimental results. For the others rare earth materials, our results are predictions.

The electronic structure and magnetic behavior of hexagonal rare-earth diboride RB 2 are studied using ab initio densityfunctional theory in the DFT þ U approach. The effect of the spin-orbit coupling is also investigated and it is found to be a necessary requirement for the accurate description of the magnetic moment. In this paper, we study the magnetic phase stability of RB 2 compounds; the band structure and the density of state (DOS) results prove that the coulomb potential and the spin-orbit interaction are keys factors to understand the magnetic properties of these series of materials. In addition, we also explain the behavior of a chemical bond of RB 2 compounds through the analysis of the DOS and of the charge density.

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