First-principles Study On The Effect Of Zr Doping On The Structure And Electronic Structure Of CeO₂（111） Surface

Cerium dioxide polishing powder has excellent polishing performance and chemical activity due to its unique electronic properties of Ce-4f.As a polishing material with excellent properties,it is widely used in polishing optical glass,picture tube,optical electronic devices and so on.Although the traditional cerium dioxide polishing powder has high polishing accuracy,good polishing quality,low pollution and long service life,its shortcomings such as uneven particle size,high viscosity,easy reunion and scratch can not be ignored.Through a lot of experiments,researchers have found that element doping of cerium dioxide polishing powder can improve its polishing performance,and Zr element doping is not only effective but also more economical and applicable.Zr doping not only makes the particles more uniform,but also improves the suspension and reduces the agglomeration.In order to further clarify the effect of Zr doping on the surface structure and electronic structure of CeO2(111),the adsorption doping of Zr atom and the adsorption migration of CeO2(111)surface system before and after Zr doping are calculated and analyzed by first principles.The main research contents and results are as follows:1.The cell model of CeO2(111)surface system was established and optimized to obtain its optimal structure and parameters.On this basis,the adsorption energies of Zr atoms at five high symmetrical sites on CeO2(111)surface were calculated,and the optimal adsorption position was found to be oxygen bridge site by comparing its size.The charge density and state density of CeO2(111)surface system before and after Zr adsorption were calculated.It was found that Zr adsorption resulted in a gap state between Ce-4f and O-2p states in the system state density diagram,which is composed of valence-changing surface Ce1 and Ce4 atoms.2.The oxygen vacancy formation energy of the surface system of reduced CeO2(111)adsorbed by Zr(Zr/CeO2-x(111))was calculated and compared with that of pure CeO2(111)surface system.It was found that the oxygen vacancy formation energy of CeO2(111)surface system was reduced by Zr adsorption.The density of states of Zr/CeO2-x(111)system is plotted.It can be seen that there are two interstitial states between Ce-4f and O-2p states,which are composed of four surface Ce atoms.3.By calculating the average formation energies of different doping forms of Zr in CeO2(111)surface system,it is found that the best doping form is to replace one surface Ce atom.The effect of Zr doping on oxygen vacancy formation energy was calculated.It was found that Zr doping reduced oxygen vacancy formation energy.The surface structure and electronic structure of Zr-doped non-reductive and reductive systems were calculated and compared with those of non-doped systems.It was found that Zr-doped system had a large disturbance to its neighboring atoms,but had no obvious effect on the density of states of the system.4.The adsorption and migration of Ce and O atoms on GeO2(111)surface system and Ce0.92Zr0.08gO2(111)surface system were calculated and compared.It was found that the doping of Zr inhibited the growth of Ce and O atoms on CeO2(111)surface resulting in grain refinement and increased specific surface area of the crystal.