The electronic structures, optical dielectric functions, elastic properties, and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation. The density of states and distribut...The electronic structures, optical dielectric functions, elastic properties, and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation. The density of states and distributions of charge density show that O and Ba tend toward ionic bond, but O and W or Zn display the covalent bond character. The calculated energy band structure shows that Ba2ZnWO6 is a wide indirect band gap semiconductor. The static value 2.28 of the refractive index is attained. The analysis of the elastic properties of Ba2ZnWO6 indicates a rather weak elastic anisotropy. The phonon dispersion is calculated, suggesting no structural instability, which is agreement with the recent low temperature neutron diffraction experiments. The mensurability Cv （phonon heat capacity） as the function of the temperature is also calculated to judge our results for future experiment.展开更多
In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10)...In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10))combinational possibilities.Considering 4 types of magnetic states,namely,ferromagnetic(FM),ferrimagnetic(FiM),antiferromagnetics(AF),and nonmagnetic(NM)with full structure optimization,13 possible surviving,stable FM/FiM-HM materials containing 6 FM-HM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),La_(2)CrNiO_(6),La_(2)VScO_(6),La_(2)VZnO_(6),and La_(2)VNiO_(6))and 7 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),La_(2)TiCoO_(6),La_(2)CrZnO_(6),La_(2)CrMnO_(6),La_(2)ScFeO_(6),and La_(2)TiMnO_(6))are found.Considering the correlation effect(GGA+U),there are 6 possible half-metallic stable,surviving(HM)materials containing 3 FMHM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),and La_(2)CrNiO_(6))and 3 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),and La_(2)TiCoO_(6)).展开更多
In the search for new materials with applicable magnetic properties in spintronic devices,the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La_(2)CoFeO_(6) using the modified Pechini rou...In the search for new materials with applicable magnetic properties in spintronic devices,the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La_(2)CoFeO_(6) using the modified Pechini route;the experimental study of structural,morphological and magnetic properties,and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional Theory.Rietveld refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure,space group P2_(1)/n(#14).Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline,with mean grain sizes between 177 and 188 nm.The dispersive X-ray spectroscopy suggests that the material obtained contains La,Fe,Co and O in the stoichiometric proportions expected by up to 98%.The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically,showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO_(6) and CoO_(6) octahedra.Magnetic hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated,up to room temperature.I-V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor type.The ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.展开更多
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2013QNA32)
文摘The electronic structures, optical dielectric functions, elastic properties, and lattice dynamics of Ba2ZnWO6 have been investigated by using the generalized gradient approximation. The density of states and distributions of charge density show that O and Ba tend toward ionic bond, but O and W or Zn display the covalent bond character. The calculated energy band structure shows that Ba2ZnWO6 is a wide indirect band gap semiconductor. The static value 2.28 of the refractive index is attained. The analysis of the elastic properties of Ba2ZnWO6 indicates a rather weak elastic anisotropy. The phonon dispersion is calculated, suggesting no structural instability, which is agreement with the recent low temperature neutron diffraction experiments. The mensurability Cv （phonon heat capacity） as the function of the temperature is also calculated to judge our results for future experiment.
基金the resource support from the Computational Materials Research Focus Group(CMRFG)the financial supports from the National Science Council(99B0320)+1 种基金the Center for General Education of National Normal Universitythe National Center for High-Performance Computing for computer time and facilities.
文摘In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10))combinational possibilities.Considering 4 types of magnetic states,namely,ferromagnetic(FM),ferrimagnetic(FiM),antiferromagnetics(AF),and nonmagnetic(NM)with full structure optimization,13 possible surviving,stable FM/FiM-HM materials containing 6 FM-HM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),La_(2)CrNiO_(6),La_(2)VScO_(6),La_(2)VZnO_(6),and La_(2)VNiO_(6))and 7 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),La_(2)TiCoO_(6),La_(2)CrZnO_(6),La_(2)CrMnO_(6),La_(2)ScFeO_(6),and La_(2)TiMnO_(6))are found.Considering the correlation effect(GGA+U),there are 6 possible half-metallic stable,surviving(HM)materials containing 3 FMHM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),and La_(2)CrNiO_(6))and 3 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),and La_(2)TiCoO_(6)).
基金This work was partially supported by Division of Investigation and Extension(DIEB)of the National University of Colombia,Hermes code 48069,MINCIENCIAS on the project FP80740-243-2019 and Coordenacao de Aperfeicoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code 001.A special thanks to Dr.Julio C.Denardim for facilitating his laboratory equipment at the University of Santiago,Chile.
文摘In the search for new materials with applicable magnetic properties in spintronic devices,the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La_(2)CoFeO_(6) using the modified Pechini route;the experimental study of structural,morphological and magnetic properties,and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional Theory.Rietveld refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure,space group P2_(1)/n(#14).Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline,with mean grain sizes between 177 and 188 nm.The dispersive X-ray spectroscopy suggests that the material obtained contains La,Fe,Co and O in the stoichiometric proportions expected by up to 98%.The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically,showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO_(6) and CoO_(6) octahedra.Magnetic hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated,up to room temperature.I-V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor type.The ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.
