LDA+U study of the electronic and magnetic properties of the Sr2FeMo1-xNbxO6 compound

DFT Electronic Properties and Synthesis Thermodynamics of Li x La1−x TiO3 Electrolytes for Li-Ion Batteries

“…8,9,13 Double-perovskite oxides AA'BO 3 or ABB'O 3 could be good candidates as electrodes or electrolytes in energy storage devices, 14 since the electronic, magnetic, mechanical and electrochemical properties can be controlled by changing the atomic species at the sites A, A′, B or B′. [15][16][17][18] Particularly, perovskite-type titanate compounds are good candidates to be used as solid-electrolytes in Li-ion batteries since they have associated ionic-conductivity values comparable to those of liquid electrolytes (e.g., LiPF 6 ). 19 Furthermore, contrasting with other inorganic solid-state materials, the perovskite-type titanate electrolytes have associated better thermodynamic and chemical stabilities at the EEI, even with different materials.…”

LDA+U study of hydrostatic pressure effect on double perovskite Sr2FeNbO6: crystal structure, mechanical and electronic properties

“…LDA+U calculations, as it is implemented in the Cambridge Serial Total Energy Package (CASTEP) code [33], were carried out on a tetragonal structure with space group I4/m (No. 87), which has been reported from experimental and theoretical works [8,9,14,15,34]. The I4/m tetragonal structure has Z=2, with Wyckoff atoms positions as follows (figure 1): Sr, 4d (1/2, 0, 1/4); Fe, 2a (0, 0, 0); Nb, 2b (0, 0, 1/2); O1, 8 h (x, y, 0); O2, 4e (0, 0, z).…”

“…It has been shown that for some concentrations of the Sr 2 FeNb 1−x Mo x O 6 double perovskites (x>0.3), it is possible to induce magnetic and electronic transitions from antiferromagnetic (AFM) to ferromagnetic (FM), and semiconductor to conduct or behaviors. Those results have been supported by density functional theory calculations, within the local density approximation and Hubbard correction (LDA+U), where it was shown the influence of Mo on the physical properties of Sr 2 FeNb 1−x Mo x O 6 compounds [14]. Then, the properties of the Sr 2 FeNbO 6 compound can be modulated in a controlled way through the doping elements.…”

“…Figures 4(a)-(f) show the density of states (DOS) from zero to 50 GPa for the Sr 2 FeNbO 6 compound. A symmetrical distribution was found in both spin channels for the pressure range studied; this is related to an electronic pairing corresponding to the AFM behavior [14]; therefore, the AFM behavior is kept. The main effect of pressure on DOS is the shift to lower energies in both spin channels.…”

“…The Hubbard parameter was implemented just for Fe atom since it behaves like Fe 3+ in Sr 2 FeNbO 6 compound, so it maintains 5 electrons in the 3d orbitals; on the other hand, the Nb remains with a 5+oxidation state, so it behaves like just the core, therefore, no U parameter is necessary for Nb atoms, similarly as happens with Mo atom in the Sr 2 FeMoO 6 compound [38]. A common value of effective Hubbard parameter for Fe (U Fe ) in double perovskites has been reported around 4 eV [38]; however, in recent studies, it has been reported that in the Sr 2 FeNbO 6 compound, an U Fe =9 eV is necessary to obtain the E g around 2 eV [14,34], therefore, an U Fe =9 eV is used. The tolerance parameters to achieve the convergence were: cut-off energy of 600 eV for the plane wave expansion, 2×10 −5 eV/atom for the energy difference, 0.05 eV Å −1 for the forces between atom pairs, 2×10 −3 Å for the ionic displacement, 0.02 GPa for stress.…”