Theoretical Studies on the EPR Parameters and Local Structures for the Orthorhombic and Tetragonal Cu2+ Centers in Cu1-xHxZr2(PO4)3

The defect structures of the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 are theoretically studied by analyzing their experimental electron paramagnetic resonance (EPR) parameters, based on the perturbation formulas of these parameters for a 3d9 ion in orthorhombically and tetragonally elongated octahedra, respectively. The above centers are attributed to the Cu2+ ions locating at M(1) site, and the crystal field parameters (CFPs) are quantitatively determined from the superposition model and the local structures of the Cu2+ sites. Based on the calculation, the parallel Cu-O bonds may undergo the relative elongations ΔZO (≈ 0.113 Å) and ΔZT (≈ 0.102 Å) for the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 along z-axis, respectively. Meanwhile, the planar Cu-O bonds are found to experience the relative variation δr (≈ 0.056 Å) along the x- and y-axes for the orthorhombical Cu2+ center because of the Jahn-Teller (JT) effect. The theoretical EPR parameters based on the above local structures agree well with the observed values.The defect structures of the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 are theoretically studied by analyzing their experimental electron paramagnetic resonance (EPR) parameters, based on the perturbation formulas of these parameters for a 3d9 ion in orthorhombically and tetragonally elongated octahedra, respectively. The above centers are attributed to the Cu2+ ions locating at M(1) site, and the crystal field parameters (CFPs) are quantitatively determined from the superposition model and the local structures of the Cu2+ sites. Based on the calculation, the parallel Cu-O bonds may undergo the relative elongations ΔZO (≈ 0.113 Å) and ΔZT (≈ 0.102 Å) for the orthorhombical and tetragonal Cu2+ centers in Cu1-xHxZr2(PO4)3 along z-axis, respectively. Meanwhile, the planar Cu-O bonds are found to experience the relative variation δr (≈ 0.056 Å) along the x- and y-axes for the orthorhombical Cu2+ center because of the Jahn-Teller (JT) effect. The theoretical EPR parameters based on the above local structures agree well with the observed values.