Exploration of the crystal structures and electronic features of Y₂O₃:Er and Y₂O₃:Er,Yb crystals: a first-principles study

Abstract The Er 3+ doped Y 2 O 3 (Y 2 O 3 :Er) and Er 3+ , Yb 3+ co-doped Y 2 O 3 (Y 2 O 3 :Er,Yb) have attracted considerable attention due to their outstanding optical properties. However, the crystal structures underlying their electronic features are still unclear. In this paper, we carried out the systematical structural evolutions of Y 2 O 3 :Er and Y 2 O 3 :Er,Yb via the Crystal Structural AnaLYsis by Particle Swarm Optimization structure search method. Two novel monoclinic structures with P2 space group were uncovered for Y 2 O 3 :Er and Y 2 O 3 :Er,Yb. Validities of the two ground state structures were verified by the good agreements between the calculated x-ray diffraction patterns and the experimental ones. Phonon dispersion curves were also investigated, and the data showed that the ground state structures of both Y 2 O 3 :Er and Y 2 O 3 :Er,Yb were dynamically stable. Moreover, the density of states, the band structure and the electronic local function of these two systems were also studied. The impurity Er 3+ and Yb 3+ ions lead to the transition of electronic feature from the insulator to the semiconductor. The Y–O, Er–O, Yb–O bonds are proved to be covalent bonds. These research results can fill up the vacancy and give instructions in the rare-earth doped laser materials in the future.