First-principle study of the microstructure and electronic properties for Cr3+ doped yttrium orthoaluminate

Abstract

Chromium ion (Cr3+) doped YAlO3 host crystal shows strong prospects for the exploitation of new optical materials. However, the microstructure of Cr3+ doped of YAlO3 is still unclear. In this work, we systematically explore the structural evolutions of Cr3+ doped of YAlO3 system by using the CALYPSO method and density functional theory. A novel cage-like structure with P-1 space group is identified for the first time. The impurity Cr3+ ion can naturally substitute the Al3+ ion of the central site in the crystal lattice. The result show that the impurity Cr3+ concentration is determined to be 6.25%, which is almost comparable to the experiments. The perfect agreement between our simulated X-ray diffraction patterns and the measured ones demonstrates the validity of the ground-state structure. The calculation of electronic band structure for Cr3+ doped YAlO3 reveals a closure of the insulator band gap, forming an energy gap of 2.94 eV. The result of electronic density of states shows that it is the impurity Cr3+ ion that leads to a transition from insulator to semiconductor. By analyzing the electron localization function of Cr3+ doped of YAlO3 crystal, we conclude that the Cr–O interaction is dominantly ionic bond. The obtained results could provide an important understanding of the transition-metal doped host materials.