DFT prediction of a novel molybdenum tetraboride superhard material

Abstract

In this work, we predict that MoB4 with monoclinic structure (C2/m) and orthorhombic structure (Immm) are potential superhard materials because of the 3D-network B–B covalent bonds. In addition, the hardness of MoB4 is attributed to the B/G ratio and c/a ratio.

Influence of alloying elements on the mechanical and thermodynamic properties of ZrB12ceramics from first‐principles calculations

“…Hard and superhard materials (≥40 GPa) are very important industrial materials, which are widely used in various industrial applications because of their high hardness, ultracompressibility, high melting point, and excellent thermal stability etc . In comparison to diamond and boron nitride ( c ‐BN), the transition metal borides (TMBs) are attractive potential superhard materials because of the network and shorter covalent bonding such as BB covalent bond and TMB bond . Diborides (TMB 2 ) and transition metal tetraborides (TMB 4 ) have been widely investigated over the last years .…”

Enhancing the Vickers hardness, melting point and thermodynamic properties of hafnium dodecaboride

“…Therefore, research has focused on the boron-rich borides such as TMB 3 , TMB 4 and TMB 12 in recent years. [17][18][19][20][21] However, the investigation of boron-rich boride faces two key problems: one is that the boron-rich boride has difficulty meeting stable conditions. For example, the published TMB 12 mainly focuses on the ZrB 12 and HfB 12 .…”

Physical Properties and Electronic Structure of Cr2B Under Pressure

“…The previous works reported that the pressure reduces the Vickers hardness of materials. [ 7,9,16,17 ] However, the Vickers hardness of Cr 2 B under P > 30 GPa increases. The reason of abnormal change of hardness under pressure will be discussed later.…”

“…Superhard metals show excellent performance, including the high hardness, wear resistance, good thermodynamic stability and metallic behavior, compared with traditional superhard materials. [ 1–9 ] The superhard metals can be synthesized by inserting strong covalent bonds of light element (LE), such as carbon, boron, nitrogen, into transition metal (TM) with a large number of valence electrons. Based on the classical thought, to obtain a high hardness, a straightforward way was to incorporate more light atoms into the transition metal to form strong covalent bonds.…”

“…However, many works indicated that the Vickers hardness decreased with the increased B / G (toughness). [ 7,9,16,17 ] Pan et al found the Vickers hardness of MoB 4 decreased with the increased pressure, while the value of B / G increased based on the ab initio calculations, [ 9 ] the same results was also found in ZrB 12 , [ 7 ] CrB 4 , [ 16 ] Ti 2 B, [ 17 ] et al Cr 2 B has the lowest boron content in binary titanium borides and possesses I4/m symmetry, which was energetically and dynamically stable. [ 15 ] In this work, we found that the high pressure increased the hardness and toughness of Cr 2 B with I4/m symmetry simultaneously.…”