Elastic anisotropies and thermal conductivities of WB2 diborides in different crystal structures: A first-principles calculation

In the present work, we performed the first-principles calculations to investigate the phase stabilities, elastic anisotropies and thermal conductivities of WB2 in hexagonal, trigonal and orthorhombic crystal structures. WB2 diborides are thermodynamically stable and the order of phase stability is hP6 > oP6 > hR9 > hR18 > hP12 > hP3. The polycrystalline elastic moduli, Poisson's ratios, hardness and Debye temperatures are calculated based on the single-crystal elastic constants. According to the mechanically stable criterions, all WB2 diborides are mechanically stable. The order of elastic anisotropy follows as hP3-WB2 > hR9-WB2 > oP6-WB2 > hP6-WB2 > hR18-WB2 > hP12-WB2. The obtained directional sound velocities also show the anisotropy of WB2. Besides, the minimum thermal conductivities of WB2 are calculated by Clarke's and Cahill's models, and the order is hP3-WB2 < hP12-WB2 < hR9-WB2 < hR18-WB2 < hP6-WB2 < oP3-WB2. Moreover, the directional minimum thermal conductivities of WB2 are anisotropic. (c) 2018 Elsevier B.V. All rights reserved.