Theoretical Explanation of the Local Structures and Spin Hamiltonian Parameters in Ca(OD)_2 of the Tetragonal Cu~(2+) Center

Based on the cluster approach,the high-order perturbation formulas for a 3d9 ion in tetragonal octahedral are established and applied to the studies of the spin Hamiltonian parameters of the g facts g|| and g⊥ and the hyperfine structure constants A|| and A⊥.In these formulas,the contributions to the g factors from the tetragonal distortion are characterized by the tetragonal field parameters Ds and Dt.Since the spin Hamiltonian parameters are sensitive to the local structure of a paramagnetic impurity center,the defect structure of Cu2+ center in Ca(OD)2 crystal is estimated,the oxygen octahedron is found to undergo the local elongation ΔZ(0.008 3 nm) along the C4 axis.Based on the above local structure,the calculated results show good agreement with the experimental data,and the defect structure of Cu2+ center in Ca(OD)2 crystal.