Investigations of the optical spectra and local structure for nickel(II) ions in XF2 (X = Mg, Zn) single crystals

A complete diagonalization energy matrix method (CDM) is proposed for 3d(8) ions in orthorhombic site (D-2h) symmetry. As an application, the optical spectra of XF2 : Ni2+ (X = Mg, Zn) is well explained on the basis of both the CDM and the semi-self-consistent field d-orbital (semi-SCF d-orbital) theory. In addition, by establishing the relationship between the optical spectra and local structure, it has been possible to calculate the crystal structure parameters for XF2:Ni2+ from optical measurements on Ni2+ ions. The theoretical results are in good agreement with experimental findings.