First-principles Calculations Of The Mechanical Properties Of New Superbard Materials ReB₂

With the rapid development of modern science and technology, there’s an increasedattention for the research of high-performance materials，super-hard material is one of them.Superhardmaterials has been widely applied to the national defense,machinery-manufacturing,aerospace and other top science. However, almost all superhard materials （diamond、cubicBN，etc） are expensive because they either occur naturally in limited supplies or have to besynthesize under harsh conditions. So it is necessary that a considerable number of theoreticaland experimental research works are committed to looking for new superhard materials. In2007, scientists of the University of California at Los Angeles successfully synthesized thesuperhard material ReB₂under simple ambient conditions. ReB₂is a new superhard material，it is impossible for ReB₂to replace the diamond in a short time，but we are sure that it willhave a bright future. The mechanical properties of ReB₂have been researched usingfirst-principles method and density functional theory in this work．We use density functional theory to calculate the lattice parameters a、c and the bulkmodulus Bo. We also calculate the elastic constantsC11、C12、C13、C33、C44, and find that it isless compressible along the c-axis than along the a-axis, i.e. the compressibility of ReB₂isanisotropic. Then，the band structure and density of state have been calculated, and theanalysis of the band structure and the density of states of ReB₂indicates that it is metallic insome degree and holds strong covalent bond. Since metallicity is uncommon in superhardmaterials, that is, most of the superhard materials are insulators or semiconductors, thisspecial characteristic of ReB₂will put it in a favorable position in the future applications, andthe strong covalent bond of ReB₂that is responsible for the high bulk modulus and largehardness.