Fully relativistic analysis of the absorption spectra of Ca₃Sc₂Ge₃O₁₂:Ni²⁺

Abstract

Systematic analysis of the energy level schemes, ground state absorption (GSA) and covalency effects for the Ni 2+ ion in Ca 3 Sc 2 Ge 3 O 12 was performed. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron method (DV-ME) [K. Ogasawara et al., Phys. Rev. B 64, 115413 (2001)] was used in the calculations. As a result, complete energy level schemes of Ni 2+ and its absorption spectra at both possible crystallographic positions (distorted octahedral Sc 3+ and tetrahedral Ge 4+ positions) were calculated, assigned and compared with experimental data. Energies of the charge transfer (CT) transitions for both positions are estimated. Numerical contributions of all possible electron configurations into the calculated energy states were determined. By performing analysis of the molecular orbitals (MO) population, it was shown that the covalency of the chemical bonds between the Ni 2+ and O 2-ions increases in passing from the hexa-to the tetra-coordinated complex.

Investigations of the optical and EPR spectra for (NiX6)4− (X=Cl, Br, I) clusters

“…The optical and electron paramagnetic resonance (EPR) spectra of the halide materials containing divalent nickel have been studied extensively over the thirty years [1][2][3][4][5][6][7][8][9]. Especially for CsMgX 3 (X ¼ Cl, Br, I) crystals, the (MgX 6 ) 4À octahedra share opposite faces to form infinite linear chains along the crystallographic c-axis.…”

Crystal field parameters of praseodymium in oxides

“…Usually, they are determined by fitting the experiment and in some cases it is difficult even to estimate a reasonable interval in which CFP should lie. The calculation of CFP is therefore desirable and several papers addressing this problem appeared recently [2][3][4]. Some years ago, we proposed a way to calculate the contribution to CFP of the electrostatic potential for the rare-earth (RE) ions [5].…”

Analysis of optical spectra of V2+ centres in ZnS and ZnSe single crystals

“…As mentioned in Refs. [33,[39][40][41][42] there exists a systematic overestimation of the energy levels obtained using the DVME method with respect to the experimental results; such an overestimation is also seen from the data of Table 4 for both crystals (compare with Tables 2 and 3). This overestimation is about 30-40 % and is due to underestimation of electron correlation [33].…”

“…To emphasize the wide applicability of the method employed in the present paper, we mention that it has been successfully applied to the systematic analysis of the energy levels and absorption spectra of trivalent lanthanides [33], calculations of the X-ray absorption near-edge structure (XANES) spectra of transition metal ions [34,35], microscopic studies of crystal field effects in impurity centres formed by 3d and 4f ions [36][37][38] and simulation of the optical absorption spectra of 3d ions [39][40][41][42].…”