Analysis of the spin–Hamiltonian parameters for Mn2+ in orthorhombic and axial symmetry sites of the alkali chlorides. Binding energies of the Mn2+ cation vacancy complexes

Abstract

The superposition model is used to analyze for the first time the second-order spin–Hamiltonian parameters b02 and b22 for the Mn2+ ion in orthorhombic C2v symmetry sites of the alkali chlorides LiCl, NaCl, KCl, and RbCl. Values for the intrinsic parameter ?2 and for the power-law exponent t2 are reported for the divalent manganese ion surrounded by chlorine ligands. In order to test the applicability of the superposition model a calculation was made of the quadrupole b02 term describing the 6S5/2 ground state splitting of the Mn2+ ion in axial symmetry sites of the alkali chlorides, using the intrinsic parameters ?2 and the power-law exponent t2 previously obtained from the analysis of the spin–Hamiltonian parameters corresponding to the orthorhombic symmetry site. In order to carry out the analysis mentioned above, a theoretical calculation was made of the lattice distortion around the impurity ion caused by its substitution for the host alkali ion in all the alkali halides. Values for the binding energy of the ground and first excited states of the impurity Mn2+ -cation vacancy pair are also reported.