Theoretical Study of the Local Lattice Distortion at the Trigonal Cr3+ Center in BiI3

Abstract

The local lattice distortion at the trigonal Cr3+ center in BiI3 is theoretically studied by the perturbation formulas of the EPR parameters for a 3d3 ion in trigonal symmetry, based on the cluster approach. In these formulas the contributions from the s-orbitals of the ligands, which were often ignored, are taken into account. It is found that the local angle β (between the direction of the impurityligand bonding R and the C3 axis) in the impurity center is smaller than the host angle βH in the pure crystal. The calculated EPR parameters are improved compared to those in absence of the ligand s-orbital contributions. The local lattice distortion obtained in this work is discussed.