Elastic anisotropy and thermodynamic properties of chromium tetraboride from first‐principles calculations

Abstract

First-principles calculations are performed to investigate the elastic anisotropy, and thermodynamic properties of chromium tetraboride (CrB 4 ) under extreme P-T conditions. The calculated equilibrium lattice and the normalized crystal parameters as a function of pressure are in good agreement with the available experimental and theoretical data. Elastic constants C ij are calculated in the pressure range of 0-50 GPa, and the bulk modulus B, shear modulus G, and Young's modulus E are also obtained according to the Voigt-ReussHill (VRH) approximation. Anisotropic indexes are employed to characterize the mechanical anisotropy. The bulk modulus and Young's modulus as a function of crystal orientations are also investigated. The obtained results suggest that CrB 4 exhibits a pronounced elastic anisotropy. It is strongest along the b-axis in response to compression loading, and the {100} and {001} shear planes might be the cleavage planes. The elastic anisotropy of CrB 4 may possibly limit its applications. Using the quasiharmonic Debye model, thermodynamic properties like Debye temperature, Gr€ uneisen parameter, heat capacity, and expansion coefficient are also systematically explored under extreme P-T conditions.

Machine Learning-Aided Exploration of Ultrahard Materials

“…The boron sheets are buckled in CrB 4 , FeB 4 , and ReB 4 but flat in MoZrB 4 , TaCrB 4 , and HfNbB 4 . The structures CrB 4 and FeB 4 were examined theoretically in refs and , respectively, where the authors reported elastic modulus values in reasonable agreement with the ones predicted by our ML models: for CrB 4 , the authors reported K = 267 GPa and G = 266 GPa versus our predicted K and G values above; for FeB 4 , the authors reported K = 277 GPa and G = 186 GPa versus our ML-predicted K = 248 GPa and G = 220 GPa. The calculated mechanical properties of TcB 4 were reported by Wang et al for which they reported Voigt moduli K = 291 GPa and G = 88 GPa, whereas our ML models predicted values K = 276 GPa and G = 203 GPa; the G values are not comparable.…”