First-principles calculations and re-analysis of optical spectra and electron paramagnetic resonance parameters for Yb³⁺ in YAl₃(BO₃)₄ crystal

In this paper, the energy levels of Yb³⁺ ions in yttrium aluminum borate (YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2k package and a traditional fitting method using a more reliable computer package. The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers. Three types of likely mistakes in the previous researcher's paper, namely over fitting, incorrect use of irreducible representation, and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper. The electron paramagnetic resonance (EPR) parameters, which included g factors like ɡ// and ɡ⊥ and hyperfine structure constants A// and A⊥, were also calculated through the perturbation method and compared with some observed values available in literature. There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation (ɡ//=4.000 and ɡ⊥=1.391; A//=1032 and A⊥=360 in 10⁻⁴ cm⁻¹ for ¹⁷¹Yb³⁺) and those from the fitting approach (ɡ//=3.612 and ɡ⊥=1.702; A//=867 and A⊥=470 in 10⁻⁴ cm⁻¹ for ¹⁷¹Yb³⁺). Copyright © 2017 The Chinese Society of Rare Earths.