First-principles study on the structure, elastic properties, hardness and electronic structure of TMB4 (TM=Cr, Re, Ru and Os) compounds

• The intrinsic hardness of CrB4 and ReB4 is bigger than 40 GPa.
• The hardness of TMB4 is calculated to be in a sequence of CrB4>ReB4>RuB4>OsB4.
• The trend of hardness for TMB4 is consistent with the variation of elastic modulus.
• The C22 value of TMB4 is bigger than that of C11 and C33.
• The high hardness of TMB4 is originated from the B–B bonds cage.

The structural formation, elastic properties, hardness and electronic structure of TMB4 (TM=Cr, Re, Ru and Os) compounds are investigated using first-principles approach. The value of C22 for these compounds is almost two times bigger than the C11 and C33. The intrinsic hardness, shear modulus and Young's modulus are calculated to be in a sequence of CrB4>ReB4>RuB4>OsB4, and the Poisson's ratio and B/G ratio of TMB4 follow the order of CrB4

The first-principles calculations show that the intrinsic hardness of CrB4 and ReB4 are bigger than 40 GPa, which are the potential superhard materials due to the B–B bonds cage structure. Figure optionsDownload as PowerPoint slide