Theoretical study on the structural,mechanical, electronic properties and QTAIM of CrB_4 as a hard material

Using the first-principles calculations based on spin density functional theory (DFT), we investigate the structure, elastic properties, and electronic structure of Pnnm-CrB₄. It is found that Pnnm-CrB₄ is thermodynamically and mechanically stable. The calculated elastic properties such as the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio indicate that CrB₄ is an incompressible material. Vicker's hardness of Pnnm-CrB₄ is estimated to be 26.3 GPa, which is in good agreement with the experimental values. The analysis of the investigated electronic properties shows that Pnnm-CrB₄ has the metallic character and there exist strong B-B and Cr-B bonds in the compound, which are further confirmed by Bader's quantum theory of atoms in molecules (QTAIM). Thermodynamic properties are also investigated.