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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 ReB2 are in excellent agreement with experimental values. The calculated bulk modulus is 361 GPa in comparison with that of the experiment. The compressibility of ReB2 is lower than that of well-known OsB2. 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 ReB2 exhibit that this material presents metallic behavior. The good metallicity and ultra-incompressibility of ReB2 might suggest its potential application as pressure-proof conductors.

The anisotropic properties of 1T- and 2H-TaS2 are investigated by the density functional theory within the framework of full-potential linearized augmented plane wave method. The band structures of 1T- and 2H-TaS2 exhibit anisotropic properties and the calculated electronic specific-heat coefficient γ of 2H-TaS2 accords well with the existing experimental value. The anisotropic frequency-dependent dielectric functions including the effect of the Drude term are analysed, where the exx(ω) spectra corresponding to the electric field E perpendicular to the z axis show excellent agreement with the measured results except for the e1xx(ω) of 1T-TaS2 below the energy level of 2.6 eV which is due to the lack of the enough CDW information for reference in our calculation. Furthermore, based on the values of optical effective mass ratio P of 1T and 2H phases it is found that the anisotropy in 2H-TaS2 is stronger than that in 1T-TaS2.

The electronic structures and optical properties of B3 ZnO series of Zn4X4-yMy(X =O, S, Se or Te; M = N, Sb, Cl or I; y = 0 or 1) are studied by first-principles calculations using a pseudopotential plane-wave method. The results show that Zn d-X p orbital interactions play an important role in the p-type doping tendency in zinc-based II-VI semiconductors. In ZnX, with increasing atomic number of X, Zn d-X p orbital interactions decrease and Zn s-X p orbital interactions increase. Additionally, substituting group-V elements for X will reduce the Zn d-X p orbital interactions while substituting group-VII elements for X will increase the Zn d-X p orbital interactions. The results also show that group-V-doped ZnX and group-VII-doped ZnX exhibit different optical behaviours due to their different orbital interaction effects.

The thermoelectric compound TiS2 is studied by using the full-potential linearized augmented plane-wave method on the density functional theory with the generalized gradient approximation (GGA) as well as the on-site Coulomb interaction correction (+U). The Seebeck coefficient of TiS2 is calculated based on the electronic structure obtained within the GGA under the consideration of the on-site Coulomb interaction. The calculated Seebeck coefficient at 300 K shows that Coulomb interaction U in the range of 4.97–5.42 eV is important to reproduce the experimental data. The obtained energy gap Eg around 0.05 eV indicates that TiS2 is an indirect narrow-gap semiconductor.