The effect of Ce-doping on the structural, electronic and magnetic properties of LiAl5O8: A first-principles study

Abstract

The host matrix LiAl5O8 doped with Ce3+ has great potential for applications in LED (light-emitting diode) and scintillators. In this work, we use ab initio calculations based on the density functional theory (DFT) to describe the effects caused by Ce dopant on the structural, electronic and magnetic properties of LiAl5O8. To evaluate where the dopant is inserted, we consider two calculation configurations: the Ce ion is inserted in the tetrahedral site (8c) and in the octahedral site (12d). To evaluate which charge of the dopant makes the system more stable, we performed the simulations considering the neutral system q ​= ​0, removing an electron q ​= ​+ 1 and adding an electron q ​= ​- 1. The Kohn-Sham equations were solved considering correlation and exchange effects described by the generalized gradient approximation (GGA) with PBE parameterization and GGA ​+ ​Ueff (Ueff ​= ​2.0 ​eV, 2.5 ​eV, and 3.0 ​eV). The lattice parameters and atomic positions have been optimized and then the local structure around the defect has been determined. Through the Bader analysis, we determine the dopant charge that makes the system more stable. The incorporation of the Ce ion in the host matrix leads to the formation of an occupied 4f state inside band gap, corresponding to a 4f electron of Ce3+. The occupied 4f state is located at 3.25 ​eV above the top of the matrix valence band. We obtained a value of approximately +1μB for the total spin magnetic moment in the unit cell for the replacement of Al3+ by Ce3+ at the octahedral site.