Theoretical Research On Optical Effect Of CeO₂with Nonmetallic Co-doping And Fe Doping Concentration

As an important the rare earth oxide,CeO₂has attracted much attention owing to the unique redox properties,strong ultraviolet absorption,structural stability,non-toxicity as well as inexpensiveness.In this paper,we will firstly introduce the research status of the optical properties on based-CeO₂materials and detailedly introduce some relevant theoretical knowledge in this article,such as Born-Oppenheimer approximation,density functional theory,generalized gradient approximation and the like,showing the influence of nonmetallic co-doping and Fe doping concentration on optical properties.Firstly,The model of nonmetallic co-doping has been built,including?N,P?,?N,S?,?C,P?,?C,S?co-doped CeO₂and calculated the materials involved in the structure,energy band,density of states,optical absorption spectrum,complex index of refraction and reflectivity.The calculated results show that:?1?for co-doped systems,larger atomic radius and less electronegativity cause the change of the lattice constants,bond length and the volume,suggesting that the structure has been distorted.It is found that co-doping results in the change of charge,which is related to the redistribution of charge.observing the bond order and the distribution maps of valence electron density,we can conclude that covalent property of N-Ce,C-Ce is stronger in comparison with that of P-Ce,S-Ce;?2?Co-doping has sharp influence on energy band structure and density of states.the energy gaps,between the valence band and the conduction band near Fermi level and from Ce4f to Ce 5d,relate to the obvious decrease.the impurity states almost overlaps with the band states,showing that that recombination center of electron-hole pairs can't been deviated.For pure CeO₂.there is the hybridization between O atoms and Ce atoms.Except the hybridization mentioned above,Ce and purity atoms participate in the hybridization,which give rise to the formation of the covalent bond.?3?Optical absorption spectrum suggest that compared with pure CeO₂,the range of the absorption Co-doped CeO₂is broade,;and co-doped CeO₂exhibits more excellent photocatalytic performance than single atom doped CeO₂.CeO₂itself has high refractive index,we calculated the refractive index and extinction coefficient,which are greatly enhanced in lower energy range and slightly increased or decreased in higher energy.Further,extinction coefficient exhibit photocatalysis in wide range because of co-doping.Interestingly,for reflectivity,the change in behavior is similar to the refractive index and extinction coefficient.Therefore,they may be considered as effective optical reflective pigments.Next,in order to learn the effect of photocatalytic behavior of doped CeO₂with different Fe concentration,we have built Fe doped CeO₂.The results show that:?1?The lattice constants,bond length and the like are relative to decrease due to smaller atomic radii,resulting in the structure distortion;?2?Density of states show the decrease of energy gap.There is the hybridization between Fe atom and O atom and Fe 3d states?either near Fermi level or near conduction band?in forbidden band;?3?making use of the real part,imaginary part of the complex dielectric function and the extinction coefficient,we know light response of doped materials and the transition of electrons.At the same time,we predict the change of optical absorption with Fe doping;?4?It is clear that CeFe₃O₈shows superior behavior by optical absorption spectrum and optical gap.Finally,we summarize the work of this paper and further predict the optical devel-opment of this material in the future,so as to achieve and promote the research in the field.