Theoretical investigations of the local distortion and electron paramagnetic resonance parameter for CdCl2:V2+ and CsMgX3:V2+ (X = Cl, Br) systems

This paper systematically investigates the local distortion and electron paramagnetic resonance (EPR) parameter for CdCl2:V2+ and CsMgX3:V2+ (X = Cl, Br) systems on the basis of the complete energy matrix, in which not only the contributions due to the spin–orbit coupling of the central ions but also that of the ligands are considered. To describe the difference of overlapping between d-orbits and p orbit, two spin–orbit coupling coefficients are introduced. By simulating the crystal field parameter and EPR parameter, the local distortion parameters are studied and the relationships between the EPR parameter and the spin–orbit coupling coefficients as well as divergent parameter are discussed. These results show that the local structures exhibit compression distortion for CdCl2:V2+ and elongation distortions for CsMgX3:V2+ (X = Cl, Br), respectively. It notes that the empirical formula R ≈ RH + (ri – rb)/2 is not suitable for CdCl2:V2+ and CsMgX3:V2+ (X = Cl, Br) systems. The contributions of ligand to spin–orbit coupling interaction cannot be neglected for strong covalent systems, especially for V2+ doped in CsMgBr3:V2+.