Theoretical studies of the EPR parameters and local structures for the two Cu 2+ centers in Cd(HCOO) 2 ·2H 2 O

Based on the studies of the electron paramagnetic resonance parameters for two types of the Cu 2+ centers in Cd(HCOO) 2 ·2H 2 O by using the high‐order perturbation formulas for a 3d 9 ion in a rhombically elongated octahedron, local structure of the doped copper ion is determined. Research suggests that the impurity Cu 2+ replaces the host Cd 2+ and undergoes the local rhombic elongation distortion, characterized by the axial elongation ratios of 4.1%, and 3.8% along the z ‐axis and the planar bond length variation ratios of 3.8%, and 3.1% along the x‐axis and y‐axis, for Cu 2+ Centers, I and II, respectively. The above slightly different axial elongation ratios and planar bond length variation ratios may suitably account for the slightly dissimilar axial g anisotropies Δ g (≈0.351 and 0.339) and perpendicular g anisotropies δ g (≈0.028 and 0.022) of the two centers, respectively.