Theoretical studies of lattice distortions around the impurity ions in V2+ doped CdCl2, CdI2 and PbI2

The lattice distortions around the impurity ions in V2+ doped CdCl2, CdI2 and PbI2 are theoretically studied from the perturbation formulas of the spin Hamiltonian (SH) parameters zero-field splitting, g factors and the hyperfine structure constants for a 3d3 ion in trigonal symmetry based on the cluster approach. In these formulas, the contributions from the s-orbitals of the ligands are taken into account. Based on the studies, it is found that the local angles β (between the impurity-ligand bonding lengths and the C3 axis) in the impurity centers are smaller than the angles βH in the hosts. The calculated SH parameters based on the above local angles β show better agreement than those on neglecting of the ligand s-orbital contributions (and those on the host angles βH) with the experimental data.