Effects of distortions in ion-host systems on optical spectra, crystal-field and spin-Hamiltonian parameters of Cr ions doped pyrochlores YTiO and YSnO: exchange charge model and superposition model calculations.

Comparative modelling of the crystal-field parameters (CFPs), CF energy levels, and effective spin-Hamiltonian parameters (SHPs), , the -factors and zero-field splitting parameter (ZFSP), , of the ground state A of the Cr dopant ions in YTiO and YSnO is carried out. The CFPs are calculated using XRD structural data by employing two semi-empirical models: the exchange charge model (ECM) and superposition model (SPM). This two-fold approach ensures increased reliability of CFP modelling and thus of the final results.