The geometrical structure and electronic properties of trivalent Ho(3+) doped Y(2)O(3) crystals: a first-principles study

Trivalent rare-earth holmium ion (Ho(3+)) doped yttrium oxide (Y(2)O(3)) has attracted great research interest owing to its unique optoelectronic properties and excellent performances in many new-type laser devices. But the crystal structures of the Ho(3+)-doped Y(2)O(3) system (Y(2)O(3) : Ho) are still unclear. Here, we have carried out a first-principle study on the structural evolution of the trivalent Ho(3+) doped Y(2)O(3) by using the CALYPSO structure search method. The results indicate that the lowest-energy structure of Ho(3+)-doped Y(2)O(3) possesses a standardized monoclinic P2 phase. It is found that the doped Ho(3+) ion are likely to occupy the sites of Y(3+) in the host crystal lattice, forming the [HoO(6)](9−) local structure with C(2) site symmetry. Electronic structure calculations reveal that the band gap value of Ho(3+)-doped Y(2)O(3) is approximately 4.27 eV, suggesting the insulating character of Y(2)O(3) : Ho system. These findings could provide fundamental insights to understand the atomic interactions in crystals as well as the information of electronic properties for other rare-earth-doped materials.