Based on the density functional theory (DFT), using linearized augmented plane wave and improved local orbital (APW+lo), the structures and energies of Y, Fe, V, FeV, YFe 12−x V x , and Y 2 Fe 17 are optimized and calculated. It is explained that the pure YFe 12 with ThMn 12 -type structure does not exist, and replacing a small fraction of vanadium can stabilize the structure. The local magnetic moments reveal that the decrease of magnetization of YFe 12−x V x does not only correspond to a simple dilution of the iron sublattice magnetization, but also reduce the Fe moments as well with increasing vanadium content. YFe 12−x V x , density functional theory (DFT), magnetic moment, stabilization PACS: 71.15.Mb, 75.10.Lp, 75.50.Bb
The lattice parameters, band structure, density of state and elastic constant of RE-doped CeO 2 (RE=Sm, Gd, Dy), the buffer material for coated HTS conductors, are calculated using the plane-wave method with pseudopotentials based on the density functional theory (DFT) of first-principle. The rule and mechanism of the effect of rare earth impurity on the critical thickness of the CeO 2 buffer layer are investigated. It is found that, in the range of the calculation, the changes of the lattice volume V and elastic constant E* of CeO 2 with the impurity are mainly determined by the increased electrons Δn e of the system. The relationship of the elastic constant E* and increased electrons Δn e is established. It is indicated that the critical thickness of the CeO 2 single buffer layer doped with Sm, Gd, and Dy may be enhanced by 22%, 43% and 33%, respectively.CeO 2 , first principle, critical thickness, elastic constantsSince the first discovery of oxide superconductors in 1986, the research on them in the material science field has proceeded, and the process developments for their applications have also started in recent years. The second generation (2G) high temperature superconducting tapes have considerable potential for large scale power applications because of their ability to carry large in-field current densities, significantly higher compared with the flowing current densities in 1G wire. However, the lack of a reliable and cost-effective process by which 2G tapes can be fabricated in the form of long length has severely hindered their development [1][2][3][4][5] . Many significant efforts for the development of coated conductors (CCs) corresponding to many industrial superconductivity applications have been made in the research fields of oxide superconductors. CeO 2 is considered one of the most effective materials as the buffer layer for CCs, with fine chemistry stability properties and little remarkable chemical reaction with YBCO. In addition, it has the matching crystal lattice with YBCO's [6,7] . Chemistry solution deposition (CSD) may be a promising cost-effective approach for the preparation of the buffer layer of CCs, moreover suitable for the long length tape. However, the thickness of CeO 2 single buffer layer prepared via CSD at present is limited to less than 50 nm [8] , or the micro crack would form in the layer. But the buffer layer thinner than 50 nm could not play the role of the diffusion barrier alone. Therefore, the thickness of CeO 2 film without crack is a significant topic in chemistry solution deposition technique. Recent years, many experiments indicated that RE (lanthanides other than Ce) doping may be an effective approach to improve the critical thickness of solution derived CeO 2 film, which
Based on density functional theory(DFT), using virtual crystal approximation and generalized gradient approximation(GGA)with pseudopotential method, the lattices and energies for five crystallines of vanadium hydrides are optimized and calculated. The phonon densities of states are calculated based on density functional perturbation theory(DFPT). The standard Heat capacities, Entropies, Helmholtz free energies and Gibbs functions of vanadium and its hydride are deduced at 298.15K. The calculated results are discussed and compared with experimental data.
In this paper, the electronic structure and photoelectric properties of P and Cu doped ZnO systems have been studied by Density functional theory method. The results show that the formation energies of ZnO-P-Cu, ZnO-P-2Cu, ZnO-P and ZnO-Cu systems decrease in turn Compared with the intrinsic ZnO system, the ZnO-P, ZnO-P-Cu, ZnO-P-2Cu and ZnO-Cu systems have higher activity, the band gap of ZnO-P and ZnO-P-2Cu systems is reduced, and the electron transition is easier. In the doped system, the peak of the dielectric function shifts to the left and increases, the absorption of the electron to the photon increases obviously, and the absorption spectrum appears red shift, from the calculated results, it can be concluded that P and Cu single-doped and co-doped ZnO have great influence on the electronic structure and optical properties of ZnO system, which provides a theoretical basis for further study of the influence of doping on the properties of ZnO.
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