Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures (original) (raw)
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Chinese Physics B, 2009
This paper investigates the structural and electronic properties of rhenium diboride by first-principles calculation based on density functional theory. The obtained results show that the calculated equilibrium structural parameters of ReB 2 are in excellent agreement with experimental values. The calculated bulk modulus is 361 GPa in comparison with that of the experiment. The compressibility of ReB 2 is lower than that of well-known OsB 2 . The anisotropy of the bulk modulus is confirmed by c/a ratio as a function of pressure curve and the bulk modulus along different axes along with the electron density distribution. The high bulk modulus is attributed to the strong covalent bond between Re-d and B-p orbitals and the wider pseudogap near the Fermi level, which could be deduced from both electron charge density distribution and density of states. The band structure and density of states of ReB 2 exhibit that this material presents metallic behavior. The good metallicity and ultra-incompressibility of ReB 2 might suggest its potential application as pressure-proof conductors.
Elastic moduli of superhard rhenium diboride
Journal of Physics D: Applied Physics, 2009
The elastic moduli of polycrystalline rhenium diboride are measured as a function of temperature between 5 and 325 K. The room temperature results show that ReB 2 has very high values for both the bulk and shear modulus, confirming the incompressible and superhard nature of this material. With decreasing temperature, the moduli increase, with a hint of softening below 50 K.
Physical Review B, 2010
The recent search for superhard materials concentrated on diborides of the 5d transition metals because of their high elastic moduli. Using density-functional theory we report a systematic study of the shear-induced irreversible structural transformations and plasticity in ReB 2 which limits its strength and hardness. The plasticity is due to breaking and rearrangement of bonds accompanied by crystal-field splitting of 5d orbitals from the stabilized to destabilized states during the finite shear that takes place at the atomic level in plastic deformation. Such effects are expected to occur also in diborides of other 5d transition metals.
Solid State Communications, 2010
We study structural, elastic, and electronic properties for three RuB 2 phases using ab initio totalenergy calculations within the density functional theory. The orthorhombic and hexagonal structures are mechanically stable. More precisely, the orthorhombic is more stable than the hexagonal form. Results of bulk modulus, which are in good agreement with experimental data, show that the considered structures are potentially highly compressible materials. This is confirmed by the calculation of the hardness, indicating that RuB 2 is an ultracompressible material, but not a superhard material.
Low-compressibility and hard materialsReB2andWB2: Prediction from first-principles study
Physical Review B, 2006
First-principle calculations are performed to investigate the structural, elastic, and electronic properties of ReB 2 and WB 2. The calculated equilibrium structural parameters of ReB 2 are consistent with the available experimental data. The calculations indicate that WB 2 in the P6 3 / mmc space group is more energetically stable under the ambient condition than in the P6/mmm. Based on the calculated bulk modulus, shear modulus of polycrystalline aggregate, ReB 2 and WB 2 can be regarded as potential candidates of ultra-incompressible and hard materials. Furthermore, the elastic anisotropy is discussed by investigating the elastic stiffness constants. Density of states and electron density analysis unravel the covalent bonding between the transition metal atoms and the boron atoms as the driving force of the high bulk modulus and high shear modulus as well as small Poisson's ratio.
Elastic Behaviour of Diborides Under High Pressure
Journal of Scientific Research, 2009
The present study deals with the elastic behaviour of diborides (BeB2, MgB2 and NbB2) under high pressure with the help of equation of state (EOS) using the elastic data reported by Islam et al. It is concluded that EOS, which are based either on quantum statistical model or pseduopotential model, only are capable of explaining high pressure behaviour of the solids under study.  Moreover the value of first order pressure derivative of bulk modulus at infinite pressure (Kinfinity) is greater than 5/3 and thus the diborides under study do not behave as Thomas-Fermi electron gas under high compression. Keywords: Equation of state; High Pressure; Diborides. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1189Â
Solid State Sciences, 2013
Based on in situ synchrotron X-ray diffraction experiments employing laser heated diamond anvil cells to investigate the reaction of rhenium and boron from the elements at high-(p, T) conditions, Re 7 B 3 was found to be extremely incompressible, with B Re7B3 ¼ 435ð14Þ GPa, making it one of the least compressible binary compounds known to date. We also have determined the previously unknown bulk modulus of Re 3 B, B Re3B ¼ 320ð15Þ GPa, and have confirmed earlier reports of the bulk modulus of ReB 2 , B ReB2 ¼ 360(18) GPa. The experimental findings were supported by density functional theory calculations, which were also employed to compute elastic stiffness coefficients and estimates for the hardness. At different high-(p, T) conditions the formation of new phases were observed.
Compressibility of AlB 2 -type transition metal diborides
Journal of Physics: Condensed Matter, 2002
The pressure behaviour of a series of transition metal borides has been studied both experimentally and by means of ab initio calculations. X-ray diffraction patterns measured up to ∼50 GPa for VB 2 and ZrB 2 show no obvious phase transition. Bulk moduli of 322 and 317 GPa, respectively, were obtained using a Murnaghan equation of state. Hartree-Fock LCCO (linear combination of crystal orbitals) calculations performed for TiB 2 have allowed its compression behaviour to be studied. The bulk modulus obtained (292 GPa) and the proposed important contribution of the interlayer interaction to the elastic behaviour under high pressure are consistent with the experimental results for the other borides.