Crystal structure and elastic properties of ZrB compared with ZrB2: A first-principles study

The existences of potential crystal structures of ZrB and ZrB2 are studied by means of first-principles molecular dynamics calculations. The face-centered cubic ZrB (space group Fm-3 m, No. 225) with lattice constant a = 4.900 Å and hexagonal ZrB2 (space group P6/mmm, No. 191) with a = 3.170 Å and c = 3.544 Å have been proved to be both mechanically and dynamically stable. The optimized lattice parameters for both ZrB and ZrB2 agree with both the experimental data and previous theoretical calculations. Basic elastic properties of ZrB compared with ZrB2 using the first-principles calculations are investigated. The bulk moduli 160.6 and 229.1 GPa, shear moduli 102.7 and 210.5 GPa, Young's moduli 253.9 and 483.5 GPa, and Poisson ratios 0.2365 and 0.1483, are obtained for ZrB and ZrB2, respectively. Density of state has been explored to discuss the difference of electronic structure between ZrB and ZrB2. The reasons of lower Young's moduli of ZrB compared with that of ZrB2 are discussed as well.