First-principles Study On Structure And Electronic Structure Of F,Si-doped CeO₂（001） Surface

CeO₂ is a typical rare earth metal oxide,belonging to fluorite structure,showing good REDOX performance.As a grinding material,CeO₂has good polishing performance,high grinding efficiency and moderate mohler hardness of powder particles,so it has been widely concerned by people.Traditional CeO₂polishing powder can no longer meet the polishing requirements of some ultra-precision parts.Many research results show that doping non-metallic elements F and Si into CeO₂can change its particle morphology and agglomeration state,affect its polishing activity,and thus improve its polishing performance.In order to further study the effect of F and Si doping on the polishing performance of CeO₂,the atomic structure and electronic structure of F and Si doped CeO₂（001）surface were calculated and studied using the first-principles DFT+U method,and the effect of CeO₂（001）surface on the atomic adsorption performance of polishing component KDP（KH₂PO₄）crystal was analyzed.The main research contents are as follows:（1）Firstly,the structure of CeO₂crystal was optimized,and the formation energies of surface and subsurface oxygen vacancies formed by CeO₂（001）plane system were calculated respectively.The results show that CeO₂（001）plane is easier to form surface oxygen vacancies.（2）Select CeO₂（001）surface for F and Si doping,calculate the doping formation energy,find the most stable doping location,and study the surface structure of F and Si doped CeO₂（001）surface system,oxygen vacancy formation energy,differential charge density,Bader charge transfer,electron state density distribution.It is found that the doping of F has no significant effect on the formation of oxygen vacancy in CeO₂（001）surface system,while the doping of Si is more favorable to the formation of oxygen vacancy in CeO₂（001）surface system,and the chemical activity of Si doped surface system is improved.（3）The adsorption energy of CeO_1.979（001）surface and F,Si doped CeO_{1.979（）001}surface for H₄PO₈at O bridge,O top,Ce bridge and Ce top was calculated to find the most stable adsorption position.The atomic structure,differential charge density,Bader charge transfer and electron state density distribution of H₄PO₈adsorbed at the most stable position of substrate were studied.It is found that the doping of F is favorable to the adsorption of H₄PO₈,while the doping of Si is unfavorable to the adsorption of H₄PO₈.F doped CeO_x（001）surface reduction system is more suitable for polishing H₄PO₈.（4）The adsorption energy of CeO_1.979（001）surface and F,Si doped CeO_1.979（001）surface for H₄PO₇at O bridge,O top,Ce bridge and Ce top was calculated to find the most stable adsorption position,and the atomic structure of the most stable position for substrate adsorption of H₄PO₇was studied.The differential charge density,Bader charge transfer and electron state density distribution of the adsorption structure were investigated.It was found that the adsorption strength of H₄PO₇and H₄PO₈on the same substrate was basically the same,but the adsorption capacity of H₄PO₈on the same substrate was greater than that of H₄PO₇.