Crystal-field splitting of the Cr4+ terms in LiAlO2 oxide crystal

Crystal field analysis of the ground and excited state absorption of a Cr4+ ion in LiAlO2 and LiGaO2 crystals

“…The adjustable parameter G was defined by fitting the calculated splittings to the experimental ones, and turned out to be 6.6195 for LiAlO 2 :Cr 4+ and 9.260 for LiGaO 2 :Cr 4+ ,which is also close to the one reported for the [CrO 4 ] 4− cluster in [28]. Finally, the energy levels obtained are listed in Tables 3 and 4, in comparison with experimental measurements [9] and results of the angular overlap model [9] and crystal field analysis based on Racah theory [13,14]. To evaluate the quality of the correspondence between the calculated and observed energy levels, the root mean squared (rms) deviation for all calculated sets of energy levels was calculated as follows:…”

“…This is due to the formation of the covalent bond between the impurity ion and ligands; the Coulomb interaction between impurity ion electrons becomes weaker. This reduction for the Cr 4+ ion is larger than, for example, for the isoelectronic V 3+ ion, for which this parameter is β=0.59 [13]. A stronger nephelauxetic effect for the Cr 4+ ion indicates a higher degree of covalency compared with trivalent vanadium, and serves as another justification for the application of the ECM for the considered cases.…”

“…(1)- (4) [13]) and β = 0.41 for LiGaO 2 :Cr 4+ , known as the nephelauxetic effect [36]-is caused by covalency. This is due to the formation of the covalent bond between the impurity ion and ligands; the Coulomb interaction between impurity ion electrons becomes weaker.…”

“…In the same way, the ESA energies were defined from data of Ref. [13] and [14]. All the data are summarized in Tables 5 and 6.…”

“…[9] used the angular overlap model (AOM) [10][11][12] to calculate the energy levels of the Cr 4+ ion. Crystal field analysis of the ground state absorption in the above-mentioned hosts by means of the Racah theory was performed in [13] and [14]. The above two models employ at least several fitting parameters that are defined a posteriori by numerically fitting the calculated energy levels to the observed ones.…”