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We have studied the structural, electronic, magnetic, thermoelectric and optical properties of the half-metal BaRuO3 using the accurate full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. The GGA[Formula: see text] approximation was also used to enhance the description of the electronic structure after calculating theoretically the Coulomb repulsion ([Formula: see text][Formula: see text]eV). The ferromagnetic (FM) phase of BaRuO3 is more stable. This result is in accordance with experimental and theoretical calculations. The calculated magnetic moments in BaRuO3 were found to arise especially from the Ru-4d state electrons. We have obtained the semiconductor gap (0.9[Formula: see text]eV) in spin-up while in spin down, the metal character was dominant, and therefore BaRuO3 has a half-metallic behavior. The thermoelectric efficiency was 0.12 at room temperature. Here we have considered only the electronic thermal conductivity, we have not included the lattice thermal conductivity. The relaxation time was assumed constant. The [Formula: see text] approximation was also used to analyze the optical properties by determining the complex dielectric function from which are derived the other parameters.

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First-principles calculations based on density functional theory (DFT) confirm the half-metallic ferromagnetism in both [Formula: see text] and [Formula: see text], and the nearly half-metallic ferromagnetism in [Formula: see text] Heusler alloys with the [Formula: see text]-type structure [Formula: see text]. The electronic band structures and density of states (DOS) calculations of the [Formula: see text] and [Formula: see text] compounds show that the spin-up electrons are metallic, whereas the spin-down bands are semiconducting with a gap of 0.47 eV and 0.53 eV, respectively, with 0.21 eV and 0.36 eV as a spin-flip gap, respectively. The [Formula: see text] and [Formula: see text] Heusler were half-metal compounds with magnetic moment of [Formula: see text] and [Formula: see text] at the equilibrium lattice constants [Formula: see text] Å and [Formula: see text] Å, respectively, which agrees with the Slater–Pauling rule, and have 100% polarization for a wide range of lattice parameters. The [Formula: see text] is a nearly half-metal (NHF) compound with magnetic moment of [Formula: see text] and 92.9% polarization at the equilibrium lattice constants [Formula: see text] Å and acquire half-metal behavior under the pressure 16.70 GPa.