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1

Exchange Charge Model for Fe^{3+}:LiAl_{5}O_{8}

100%

Vaida M., Avram C.

Acta Physica Polonica A

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2009

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vol. 116

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issue 4

541-543

EN

The aim of this paper is the theoretical investigation of Fe^{3+} doped in the ordered phase of LiAl_{5}O_8. We used the shell model and pair potential approximation to optimize the geometric structure of LiAl_{5}O_{8}. This approach enables the modeling of the crystal field parameters of LiAl_{5}O_8 and then calculates the energy levels scheme of Fe^{3+} ions doped in tetrahedral sites in the title crystal. Consistent crystal field analysis and the energy level splittings for LiAl_{5}O_{8} doped with Fe^{3+} ions was performed in the frame of the exchange charge model of crystal field. The comparison of the theoretically obtained results for energy levels with the experimental data, yields satisfactory agreement and confirms the validity of the exchange charge model.

2

Geometry of the ^4T_{2g} Excited State in Cs_2SiF_6:Mn^{4+}

100%

Reisz A., Avram C.

Acta Physica Polonica A

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2007

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vol. 112

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issue 5

829-833

EN

The aim of this paper is to calculate the equilibrium displacements of the ^4T_{2g} potential surface minimum from the ground state along the a_{1g} and e_g Jahn-Teller active modes for the octahedral [MnF_6]^{2-} cluster obtained by doping Mn^{4+} ions in Cs_2SiF_6 host crystal. The equilibrium displacements in normal and Cartesian coordinates were estimated from force constants of [MnF_6]^{2-} cluster and Huang-Rhys factors associated with the Jahn-Teller stabilization energy. A net equatorial expansion and an axial stretching of the geometry of the [MnF_6]_{2-} cluster in first ^4T_{2g} excited state, as combined effect of the a_{1g} and e_g displacements, were demonstrated.

3

Crystal Field Analysis of Cr^{3+} Energy Levels in LiGa_5O_8 Spinel

81%

Brik M., Avram N., Avram C.

Acta Physica Polonica A

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2007

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vol. 112

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issue 5

1055-1060

EN

Detailed and consistent crystal field analysis of the LiGa_5O_8:Cr^{3+} absorption spectrum is performed in the present paper by using the exchange charge model of crystal field. We calculate the crystal field parameters from the crystal structure date and diagonalize the crystal field Hamiltonian to obtain the energy level structure of Cr^{3+} ions in LiGa_5O_8. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data; good agreement was demonstrated.

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3 Acta Physica Polonica A

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1 Reisz A.

1 Vaida M.

Exchange Charge Model for Fe^{3+}:LiAl_{5}O_{8}

Geometry of the ^4T_{2g} Excited State in Cs_2SiF_6:Mn^{4+}

Crystal Field Analysis of Cr^{3+} Energy Levels in LiGa_5O_8 Spinel