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In this paper we carried out the ab initio calculations of the impurity centers Y3Al5O12: R3+ (R= La-Lu) by investigation doped crystal structure and its elastic properties. The crystal structure of impurity centers was investigated and the elastic constants of the crystals RE3Al5O12 (RE = Y, La-Lu) were calculated. The effect of hydrostatic pressure on the elastic properties of RE3Al5O12 (RE = Y, La-Lu) was investigated also. Ab initio calculations were performed in periodic CRYSTAL code within the framework of the MO LCAO approach by using hybrid DFT functionals. The results obtained can be used to interpret experimental data and predict the new properties of YAG: R3+ laser materials. [ABSTRACT FROM AUTHOR]

In the present paper, we report on analysis of fine structure of energy levels of Cr3+ in octahedral and trigonal crystal field of host matrix KMgF3. The fine structure of the energy levels of the studied system was obtaining by diagonalization of Cr3+ Hamiltonian, which take into account the crystal field parameters, spin-orbit interaction and vibronic interaction. Due to vibronic interaction in 4T2g first excited state of impurity ion the Jahn-Teller effect should be considered in modeling the optical spectra of Cr3+:KMgF3. The results complete that previously obtained ones by taking into account an average reduction factor due to the covalence. [ABSTRACT FROM AUTHOR]

The crystal structure of the ytterbium hexameric cluster in CaF2 has been calculated in the framework of the embedded—cluster method within the shell model, in pair potential approximation. The crystal field parameters and scheme of the energy levels for Yb6F36 hexameric cluster were calculated in the exchange charges model. Also, the optical spectra of Yb3+ single center in CaF2 (cubic and tetragonal symmetry) was calculated and discussed. [ABSTRACT FROM AUTHOR]

The crystal structure of the ytterbium hexameric cluster in CaF2 has been calculated in the framework of the embedded—cluster method within the shell model, in pair potential approximation. The crystal field parameters and scheme of the energy levels for Yb6F36 hexameric cluster were calculated in the exchange charges model. Also, the optical spectra of Yb3+ single center in CaF2 (cubic and tetragonal symmetry) was calculated and discussed. [ABSTRACT FROM AUTHOR]