Implications of direct conversions of crystal field parameters into zero-field splitting ones - Case study: Superposition model analysis for Cr3+ ions at orthorhombic sites in LiKSO4

Abstract

Superposition model (SPM) is applied to zero field splitting (ZFS) parameters (ZFSPs) and independently to crystal field parameters (CFPs). The previous SPM/CF modeling (valid but based on early structural data) and subsequent ZFSP calculations (physically invalid) for Cr3+ ions in LiKSO4 are revisited and extended. Implications of invalid conversions of CFPs to ZFSPs, arising from mixing up the CF and ZFS quantities, are exposed. This invalid procedure based on the CF = ZFS confusion is avoided by independent SPM/ZFS modeling for Cr3+:LiKSO4 utilizing more recent structural data. Two substitutional sites, K+ and Li+, for Cr3+ ion entering LiKSO4 crystal and several distortion models are considered. The predicted ZFSPs match well experimental EMR ones. Orthorhombic standardization of ZFSPs and maximum rhombicity ratio are discussed. SPM-calculated CFPs are used as input for CF analysis package to obtain Hada optical energy bands for Cr3+ in LiKSO4. Microscopic spin Hamiltonian theory of ZFSPs in conjunction with SPM/ZFS and SPM/CF approaches enable to consider correlation of optical and EMR spectroscopy data. Overall results indicate that Cr3+ ions enter LiKSO4 lattice at K+ sites.